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Cao J, Xia J, Li X, Li Y, Liu P, Tian L, Qiao P, Liu C, Wang Y, Meng X. Defect-Mediated Growth of Crystallographic Shear Plane. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2302365. [PMID: 37420328 DOI: 10.1002/smll.202302365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 05/17/2023] [Indexed: 07/09/2023]
Abstract
As representative extended planar defects, crystallographic shear (CS) planes, namely Wadsley defects, play an important role in modifying the physical and chemical properties of metal oxides. Although these special structures have been intensively investigated for high-rate anode materials and catalysts, it is still experimentally unclear how the CS planes form and propagate at the atomic scale. Here, the CS plane evolution in monoclinic WO3 is directly imaged via in situ scanning transmission electron microscope. It is found that the CS planes nucleate preferentially at the edge step defects and proceed by the cooperative migration of WO6 octahedrons along particular crystallographic orientations, passing through a series of intermediate states. The local reconstruction of atomic columns tends to form (102) CS planes featured with four edge-sharing octahedrons in preference to the (103) planes, which matches well with the theoretical calculations. Associated with the structure evolution, the sample undergoes a semiconductor-to-metal transition. In addition, the controlled growth of CS planes and V-shaped CS structures can be achieved by artificial defects for the first time. These findings enable an atomic-scale understanding of CS structure evolution dynamics.
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Affiliation(s)
- Jianyu Cao
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
- School of Future Technology, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jing Xia
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Xuanze Li
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Yuye Li
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Pei Liu
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Lifeng Tian
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Peiyu Qiao
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Chang Liu
- Institute for Computational Materials Science, Joint Center for Theoretical Physics, School of Physics and Electronics, Henan University, Kaifeng, 475004, China
| | - Yifan Wang
- Institute of Process Engineering, Chinese Academy of Sciences, Beijing, 100190, China
| | - Xiangmin Meng
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
- School of Future Technology, University of Chinese Academy of Sciences, Beijing, 100049, China
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2
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Xue S, Li Phuah X, Jian J, Li Q, Li J, Yang B, Zhang D, Wang H, Tsakalakos T, Mukherjee AK, Wang H, Zhang X. In situ studies on defect formation dynamics in flash-sintered TiO 2. NANOSCALE 2023; 15:16752-16765. [PMID: 37817681 DOI: 10.1039/d3nr02630b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/12/2023]
Abstract
Flash-sintered (FS) ceramics have shown promising mechanical deformability at room temperature compared to conventional sintered ceramics. One major contributing factor to plasticity is high-density defects, such as dislocations, stacking faults and point defects, resulted presumably from the high electrical field during flash sintering. However, such direct experiemtnal evidence for defect formation and evolution under the electric field remains lacking. Here we performed in situ biasing experiments in FS and conventionally sintered (CS) polycrystalline TiO2 in a transmission electron microscope (TEM) to compare the defect evolution dynamics. In situ TEM studies revealed the coalescence of point defects under the electrical field in both FS and CS TiO2 and the subsequent formation of stacking faults, which are often referred to as Wadsley defects. Surprisingly, under the electrical field, the average fault growth rate in the FS samples is 10 times as much as that in the CS TiO2. Furthermore, the Magnéli phase, a 3D oxygen-deficient phase formed by the aggregation of Wadsley defects, is observed in the FS samples, but not in the CS samples. The present study provides new insights into defect dynamics in FS ceramics.
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Affiliation(s)
- Sichuang Xue
- StateKey Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China.
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA.
| | - Xin Li Phuah
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA.
| | - Jie Jian
- Institute of Special Environments Physical Sciences, Harbin Institute of Technology, Shenzhen, 518055, P.R. China
| | - Qiang Li
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA.
| | - Jin Li
- Institute of Special Environments Physical Sciences, Harbin Institute of Technology, Shenzhen, 518055, P.R. China
| | - Bo Yang
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA.
| | - Di Zhang
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA.
| | - Han Wang
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA.
| | - Thomas Tsakalakos
- Department of Materials Science and Engineering, Rutgers University, New Brunswick, NJ 08901, USA
| | - Amiya K Mukherjee
- Department of Materials Science and Engineering, University of California, Davis, CA 95616, USA
| | - Haiyan Wang
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA.
- School of Electrical and Computer Engineering, West Lafayette, IN 47907, USA.
| | - Xinghang Zhang
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA.
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3
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Green AJ, Driscoll EH, Lakhdar Y, Kendrick E, Slater PR. Structural and electrochemical insights into novel Wadsley Roth Nb 7Ti 1.5Mo 1.5O 25 and Ta 7Ti 1.5Mo 1.5O 25 anodes for Li-ion battery application. Dalton Trans 2023; 52:13110-13118. [PMID: 37675851 DOI: 10.1039/d3dt02144k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/08/2023]
Abstract
Niobium based anodes are gaining increasing popularity for application in high-power lithium-ion batteries, due to their high theoretical capacities, inherent safety at high current densities, and long-term stability. Here, we report the discovery and characterisation of a new Wadsley Roth niobate system, Nb7Ti1.5Mo1.5O25, showing that it is isostructural with known systems: Nb9PO25 and Nb9VO25. To evaluate the material's electrochemical performance, including performance at high current densities (for potential high power applications), and long-term stability, Li half-coin cells were prepared. The material showed an initial capacity of 268(9) mA h g-1 at 0.01 A g-1 (voltage range of 2.5-1.0 V). However, in subsequent cycles, some of this initial capacity is lost, which is attributed to Li trapping associated with the presence of reducible MoO4 units, similar to the situation observed for isostructural Nb9VO25. After this initial irreversible capacity loss, the material showed good performance at high current density rates, such that at 2 A g-1 and 4 A g-1 respective capacities of 132(10) mA h g-1 and 115(14) mA g-1 were delivered. Moreover, the material showed respectable capacity retention (97%) after being cycled for 100 cycles at 0.2 A g-1. In order to identify the different Nb, Ti, Mo redox couples involved in this system, a Ta analogue was also synthesized (Ta7Ti1.5Mo1.5O25) and the electrochemical performance for this phase is also reported. This phase shows a lower initial capacity at 0.01 A g-1 (140(3) mA h g-1) than the Nb analogue in the same voltage range, which can be increased (225 mA h g-1) if a lower cutoff voltage (0.5 V) is applied. The capacity retention for this Ta system after 100 cycles at 0.2 A g-1 is similar to the Nb analogue (97%). Further work has explored whether the Nb-Ti-Mo contents could be varied, and these results showed that single phase Nb10-2xTixMoxO25 samples could be prepared for 1.5 ≤ x ≤ 1.75, and electrochemical testing results for the x = 1.75 endmember are also reported. Overall, this research highlights the synthesis and electrochemical characterisation of two new Wadsley Roth phases, and further highlights the challenges associated with the presence of reducible cations in tetrahedral sites in such structures with respect to minimising initial irreversible capacity loss.
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Affiliation(s)
- A J Green
- School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
| | - E H Driscoll
- School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham, B15 2SE, UK
| | - Y Lakhdar
- School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham, B15 2SE, UK
| | - E Kendrick
- School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham, B15 2SE, UK
| | - P R Slater
- School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
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4
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Hodeau JL, Marezio M. Correlation between the twinning process and oxygen insertion in CeNbO4+x phases. J SOLID STATE CHEM 2022. [DOI: 10.1016/j.jssc.2022.123783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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5
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Wyckoff KE, Kaufman JL, Baek SW, Dolle C, Zak JJ, Bienz J, Kautzsch L, Vincent RC, Zohar A, See KA, Eggeler YM, Pilon L, Van der Ven A, Seshadri R. Metal-Metal Bonding as an Electrode Design Principle in the Low-Strain Cluster Compound LiScMo 3O 8. J Am Chem Soc 2022; 144:5841-5854. [PMID: 35333056 DOI: 10.1021/jacs.1c12070] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Electrode materials for Li+-ion batteries require optimization along several disparate axes related to cost, performance, and sustainability. One of the important performance axes is the ability to retain structural integrity though cycles of charge/discharge. Metal-metal bonding is a distinct feature of some refractory metal oxides that has been largely underutilized in electrochemical energy storage, but that could potentially impact structural integrity. Here LiScMo3O8, a compound containing triangular clusters of metal-metal bonded Mo atoms, is studied as a potential anode material in Li+-ion batteries. Electrons inserted though lithiation are localized across rigid Mo3 triangles (rather than on individual metal ions), resulting in minimal structural change as suggested by operando diffraction. The unusual chemical bonding allows this compound to be cycled with Mo atoms below a formally +4 valence state, resulting in an acceptable voltage regime that is appropriate for an anode material. Several characterization methods including potentiometric entropy measurements indicate two-phase regions, which are attributed through extensive first-principles modeling to Li+ ordering. This study of LiScMo3O8 provides valuable insights for design principles for structural motifs that stably and reversibly permit Li+ (de)insertion.
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Affiliation(s)
- Kira E Wyckoff
- Materials Department and Materials Research Laboratory, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Jonas L Kaufman
- Materials Department and Materials Research Laboratory, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Sun Woong Baek
- Mechanical and Aerospace Engineering Department, Henry Samueli School of Engineering and Applied Science, University of California Los Angeles, Los Angeles, California 90095, United States
| | - Christian Dolle
- Laboratory for Electron Microscopy, Microscopy of Nanoscale Structures and Mechanisms, Karlsruhe Institute of Technology, Engesserstraße 7, 76131 Karlsruhe, Germany
| | - Joshua J Zak
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Jadon Bienz
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Linus Kautzsch
- Materials Department and Materials Research Laboratory, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Rebecca C Vincent
- Materials Department and Materials Research Laboratory, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Arava Zohar
- Materials Department and Materials Research Laboratory, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Kimberly A See
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Yolita M Eggeler
- Laboratory for Electron Microscopy, Microscopy of Nanoscale Structures and Mechanisms, Karlsruhe Institute of Technology, Engesserstraße 7, 76131 Karlsruhe, Germany
| | - Laurent Pilon
- Mechanical and Aerospace Engineering Department, Henry Samueli School of Engineering and Applied Science, University of California Los Angeles, Los Angeles, California 90095, United States.,California NanoSystems Institute and Institute of the Environment and Sustainability, University of California Los Angeles, Los Angeles, California 90095, United States
| | - Anton Van der Ven
- Materials Department and Materials Research Laboratory, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Ram Seshadri
- Materials Department and Materials Research Laboratory, University of California Santa Barbara, Santa Barbara, California 93106, United States.,Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
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6
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Yang Y, Zhao J. Wadsley-Roth Crystallographic Shear Structure Niobium-Based Oxides: Promising Anode Materials for High-Safety Lithium-Ion Batteries. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:e2004855. [PMID: 34165894 PMCID: PMC8224428 DOI: 10.1002/advs.202004855] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 01/20/2021] [Indexed: 05/05/2023]
Abstract
Wadsley-Roth crystallographic shear structure niobium-based oxides are of great interest in fast Li+ storage due to their unique 3D open tunnel structures that offer facile Li+ diffusion paths. Their moderate lithiation potential and reversible redox couples hold the great promise in the development of next-generation lithium-ion batteries (LIBs) that are characterized by high power density, long lifespan, and high safety. Despite these outstanding merits, there is still extensive advancement space for further enhancing their electrochemical kinetics. And the industrial feasibility of Wadsley-Roth crystallographic shear structure niobium-based oxides as anode materials for LIBs requires more systematic research. In this review, recent progress in this field is summarized with the aim of realizing the practical applications of Wadsley-Roth phase anode materials in commercial LIBs. The review focuses on research toward the crystalline structure analyses, electrochemical reaction mechanisms, modification strategies, and full cell performance. In addition to highlighting the current research advances, the outlook and perspective on Wadsley-Roth anode materials is also concisely provided.
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Affiliation(s)
- Yang Yang
- School of Chemical Engineering and Light IndustryGuangdong University of TechnologyGuangzhou510006P. R. China
| | - Jinbao Zhao
- State Key Lab of Physical Chemistry of Solid SurfacesState‐Province Joint Engineering Laboratory of Power Source Technology for New Energy VehicleCollege of Chemistry and Chemical EngineeringXiamen UniversityXiamen361005P. R. China
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7
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Aalling-Frederiksen O, Juelsholt M, Anker AS, Jensen KMØ. Formation and growth mechanism for niobium oxide nanoparticles: atomistic insight from in situ X-ray total scattering. NANOSCALE 2021; 13:8087-8097. [PMID: 33956920 PMCID: PMC8101635 DOI: 10.1039/d0nr08299f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 03/14/2021] [Indexed: 06/08/2023]
Abstract
Understanding the mechanisms for nanoparticle nucleation and growth is crucial for the development of tailormade nanomaterials. Here, we use X-ray total scattering and Pair Distribution Function analysis to follow the formation and growth of niobium oxide nanoparticles. We study the solvothermal synthesis from niobium chloride in benzyl alcohol, and through investigations of the influence of reaction temperature, a formation pathway can be suggested. Upon dissolution of niobium chloride in benzyl alcohol, octahedral [NbCl6-xOx] complexes form through exchange of chloride ligands. Heating of the solution results in polymerization, where larger clusters built from multiple edge-sharing [NbCl6-xOx] octahedra assemble. This leads to the formation of a nucleation cluster with the ReO3 type structure, which grows to form nanoparticles of the Wadsley-Roth type H-Nb2O5 structure, which in the bulk phase usually only forms at high temperature. Upon further growth, structural defects appear, and the presence of shear-planes in the structure appears highly dependent on nanoparticle size.
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Affiliation(s)
| | - Mikkel Juelsholt
- Department of Chemistry and Nano-Science Center, University of Copenhagen2100 Copenhagen ØDenmark
| | - Andy S. Anker
- Department of Chemistry and Nano-Science Center, University of Copenhagen2100 Copenhagen ØDenmark
| | - Kirsten M. Ø. Jensen
- Department of Chemistry and Nano-Science Center, University of Copenhagen2100 Copenhagen ØDenmark
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8
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Du H, Jia CL, Mayer J. Local crystallographic shear structures in a[201] extended mixed dislocations of SrTiO 3 unraveled by atomic-scale imaging using transmission electron microscopy and spectroscopy. Faraday Discuss 2019; 213:245-258. [PMID: 30371713 DOI: 10.1039/c8fd00102b] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Recently, extended mixed dislocations were observed at a [001]/(100) low-angle tilt grain boundary of a SrTiO3 bicrystal because of a slight twist between the two crystal parts. The b = a[201]/(100) mixed dislocations at the grain boundary dissociate into three dislocations with Burgers vector b of a/2[101], a[100], and a/2[101], respectively. A structure model has been proposed in particular for the dislocation cores of the two partials with b = a/2[101] based on the high-angle annular dark-field (HAADF) images acquired by scanning transmission electron microscopy (STEM). However, the details of the atomic structure and the chemical composition of the dislocation cores remain unexplored, especially for the b = a[100] dislocation that is evidently disassociated into two b = a/2[101] partial dislocations. In this work, we study the further atomic details of the extended mixed dislocations, in particular the local chemistry, in a SrTiO3 bicrystal using STEM, electron energy loss spectroscopy (EELS), and energy dispersive X-ray (EDX) spectroscopy techniques. By these atomic-scale imaging techniques, we reveal a unique feature for the atomic structure of the b = a[201]/(100) extended mixed dislocation, which we named as local crystallographic shear (LCS) structures. In addition, we identify a rock salt FCC-type TiOx (x = 0.66-1.24) phase at the locations of the extended mixed dislocations. In contrast to the insulating TiO2 phases, the TiOx phase is known to exhibit very low electrical resistivity of only several μΩ cm. In this regard, the extended mixed dislocations of SrTiO3 comprising the FCC TiOx phase may function as the conducting filament in resistive switching processes by completion and disruption of the TiOx phase along the dislocation cores through electrically stimulated redox reactions.
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Affiliation(s)
- Hongchu Du
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Jülich Research Centre, Jülich, 52425, Germany.
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9
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Joos M, Cerretti G, Veremchuk I, Hofmann P, Frerichs H, Anjum DH, Reich T, Lieberwirth I, Panthöfer M, Zeier WG, Tremel W. Spark Plasma Sintering (SPS)-Assisted Synthesis and Thermoelectric Characterization of Magnéli Phase V 6O 11. Inorg Chem 2018; 57:1259-1268. [PMID: 29323485 DOI: 10.1021/acs.inorgchem.7b02669] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The Magnéli phase V6O11 was synthesized in gram amounts from a powder mixture of V6O11/V7O13 and vanadium metal, using the spark plasma sintering (SPS) technique. Its structure was determined with synchrotron X-ray powder diffraction data from a phase-pure sample synthesized by conventional solid-state synthesis. A special feature of Magnéli-type oxides is a combination of crystallographic shear and intrinsic disorder that leads to relatively low lattice thermal conductivities. SPS prepared V6O11 has a relatively low thermal conductivity of κ = 2.72 ± 0.06 W (m K)-1 while being a n-type conductor with an electrical conductivity of σ = 0.039 ± 0.005 (μΩ m)-1, a Seebeck coefficient of α = -(35 ± 2) μV K-1, which leads to a power factor of PF = 4.9 ± 0.8 × 10-5W (m K2)-1 at ∼600 K. Advances in the application of Magnéli phases are mostly hindered by synthetic and processing challenges, especially when metastable and nanostructured materials such as V6O11 are involved. This study gives insight into the complications of SPS-assisted synthesis of complex oxide materials, provides new information about the thermal and electrical properties of vanadium oxides at high temperatures, and supports the concept of reducing the thermal conductivity of materials with structural building blocks such as crystallographic shear (CS) planes.
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Affiliation(s)
- Markus Joos
- Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität , Duesbergweg 10-14, D-55099 Mainz, Germany
| | - Giacomo Cerretti
- Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität , Duesbergweg 10-14, D-55099 Mainz, Germany
| | - Igor Veremchuk
- Max Planck Institute for Chemical Physics of Solids , Nöthnitzer Str. 40, D-01187 Dresden, Germany
| | - Patrick Hofmann
- Physikalisch-Chemisches Institut, Justus-Liebig-Universität Gießen , Heinrich-Buff-Ring-17, 35392 Gießen, Germany
| | - Hajo Frerichs
- Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität , Duesbergweg 10-14, D-55099 Mainz, Germany
| | - Dalaver H Anjum
- Imaging and Characterization Core Lab, King Abdullah University of Science and Technology , Thuwal 23955-6900, Saudi Arabia
| | - Tobias Reich
- Institut für Kernchemie, Johannes Gutenberg-Universität , Fritz-Straßmann-Weg 2, 55128 Mainz, Germany
| | - Ingo Lieberwirth
- Max Planck Institute for Polymer Research , Ackermannweg 10, D-55128 Mainz, Germany
| | - Martin Panthöfer
- Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität , Duesbergweg 10-14, D-55099 Mainz, Germany
| | - Wolfgang G Zeier
- Physikalisch-Chemisches Institut, Justus-Liebig-Universität Gießen , Heinrich-Buff-Ring-17, 35392 Gießen, Germany
| | - Wolfgang Tremel
- Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität , Duesbergweg 10-14, D-55099 Mainz, Germany
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10
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Park SW, Mizoguchi H, Hiraka H, Ikeda K, Otomo T, Hosono H. Transformation of the Chromium Coordination Environment in LaCrAsO Induced by Hydride Doping: Formation of La 2Cr 2As 2O yH x. Inorg Chem 2017; 56:13642-13645. [PMID: 29083884 DOI: 10.1021/acs.inorgchem.7b02316] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report the synthesis of La2Cr2As2OyHx (0.1 < y < 1.6) oxyhydride solid solutions using a solid-state reaction under high pressure with a solid-state hydrogen source and exhibit an example of how H- doping can also promote structural changes: H- doping in LaCrAsO results in the formation of La2Cr2As2OyHx with the La2Fe2Se2O3-type layered structure. Remarkably, this transformation includes a change of the coordination number of Cr from 4 to 6, with the some of the H- being accommodated in new sites within the CrAs layers. In this way, H- not only serves as a conventional electron dopant by the substitution of O2- but also makes new bonds to the transition metals.
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Affiliation(s)
- Sang-Won Park
- Materials and Structures Laboratory and Materials Research Center for Element Strategy, Tokyo Institute of Technology , 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Hiroshi Mizoguchi
- Materials and Structures Laboratory and Materials Research Center for Element Strategy, Tokyo Institute of Technology , 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Haruhiro Hiraka
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK) , Tsukuba, Ibaraki 305-0801, Japan
| | - Kazutaka Ikeda
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK) , Tsukuba, Ibaraki 305-0801, Japan
| | - Toshiya Otomo
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK) , Tsukuba, Ibaraki 305-0801, Japan
| | - Hideo Hosono
- Materials and Structures Laboratory and Materials Research Center for Element Strategy, Tokyo Institute of Technology , 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.,ACCEL Program, Japan Science and Technology Agency , 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
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11
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Gilliard KL, Seebauer EG. Manipulation of native point defect behavior in rutile TiO 2 via surfaces and extended defects. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:445002. [PMID: 28862156 DOI: 10.1088/1361-648x/aa89ba] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Semiconductor surfaces offer efficient pathways for exchanging native point defects with the underlying bulk. For rutile TiO2(1 1 0), isotopic self-diffusion studies of oxygen have suggested that the surface may act as a source for Oi while simultaneously acting as a sink for titanium interstitials Tii. Through self-diffusion measurements with labeled Ti as well as O, the present work develops a more complete picture of the diffusion-reaction network involving Oi and Tii, complete with the surface acting as a source for whichever elements are available from the gas phase and a sink for elements that are not. The picture points to the importance of extended defects such as platelets and crystallographic shear planes as reservoirs of Oi and Tii, acting as net sources or sinks of these species depending upon specific conditions. The results exemplify the combined roles of surfaces and extended defects in regulating point defect behavior even in macroscopic metal oxide crystals, and point to specific strategies for manipulating that behavior intentionally.
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Affiliation(s)
- Kandis Leslie Gilliard
- Department of Chemical and Biomolecular Engineering, University of Illinois, Urbana, IL 61801, United States of America
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12
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Griffith KJ, Senyshyn A, Grey CP. Structural Stability from Crystallographic Shear in TiO 2-Nb 2O 5 Phases: Cation Ordering and Lithiation Behavior of TiNb 24O 62. Inorg Chem 2017; 56:4002-4010. [PMID: 28319367 DOI: 10.1021/acs.inorgchem.6b03154] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The host structure and reversible lithium insertion and extraction of an intercalation compound, TiNb24O62, are described. Neutron diffraction, applied for the first time to TiNb24O62, allowed an accurate refinement of the complex block superstructure, particularly with respect to the oxygen sublattice. Analysis of the transition-metal sites revealed significant cation ordering in the mixed-metal oxide. Electrochemical analysis demonstrated highly reversible lithium intercalation with ca. 190 mA·h·g-1 after 100 cycles (C/10 rate, 3 months). The effect of the potential window on the capacity, polarization, and reversibility was carefully examined; a minimum voltage limit of 1.1-1.2 V is critical for efficient and reversible cycling. The galvanostatic intermittent titration technique revealed three solid-solution regions, with different lithium diffusivities, in addition to the two-phase plateau that was clearly observed in the V versus Q discharge/charge profile. Lithium-ion diffusion decreases by over 3 orders of magnitude from the dilute lithium limit early in the discharge to the lithium-stuffed phase Li37.5(1.0)TiNb24O62. Nevertheless, prior to lithium stuffing, TiNb24O62 possesses intrinsically rapid lithium-ion kinetics, as demonstrated by the high-rate performance in thick films of ca. 10 μm particles when interfaced with a carbon-coated aluminum foil substrate. The TiO2·Nb2O5 phase diagram is examined and electrochemical results are compared to related superstructures of crystallographically sheared blocks of octahedra in the TiO2·Nb2O5 homologous series including the H-Nb2O5 end member.
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Affiliation(s)
- Kent J Griffith
- Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Anatoliy Senyshyn
- Heinz Maier-Leibnitz Zentrum, Technische Universität München , Lichtenbergstrasse 1, 85748 Garching bei München, Germany
| | - Clare P Grey
- Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, United Kingdom
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13
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Jia J, Qian C, Dong Y, Li YF, Wang H, Ghoussoub M, Butler KT, Walsh A, Ozin GA. Heterogeneous catalytic hydrogenation of CO2by metal oxides: defect engineering – perfecting imperfection. Chem Soc Rev 2017. [DOI: 10.1039/c7cs00026j] [Citation(s) in RCA: 229] [Impact Index Per Article: 32.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
In this review, we discuss how metal oxides with designed defects can be synthesized and engineered, to enable heterogeneous catalytic hydrogenation of gaseous carbon dioxide to chemicals and fuels.
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Affiliation(s)
- Jia Jia
- Solar Fuels Team and Materials Chemistry Group
- Department of Chemistry
- University of Toronto
- Toronto
- Canada
| | - Chenxi Qian
- Solar Fuels Team and Materials Chemistry Group
- Department of Chemistry
- University of Toronto
- Toronto
- Canada
| | - Yuchan Dong
- Solar Fuels Team and Materials Chemistry Group
- Department of Chemistry
- University of Toronto
- Toronto
- Canada
| | - Young Feng Li
- Solar Fuels Team and Materials Chemistry Group
- Department of Chemistry
- University of Toronto
- Toronto
- Canada
| | - Hong Wang
- Solar Fuels Team and Materials Chemistry Group
- Department of Chemistry
- University of Toronto
- Toronto
- Canada
| | - Mireille Ghoussoub
- Solar Fuels Team and Materials Chemistry Group
- Department of Chemistry
- University of Toronto
- Toronto
- Canada
| | | | - Aron Walsh
- Department of Materials
- Imperial College London
- London
- UK
| | - Geoffrey A. Ozin
- Solar Fuels Team and Materials Chemistry Group
- Department of Chemistry
- University of Toronto
- Toronto
- Canada
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14
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Perfler L, Kahlenberg V, Wikete C, Schmidmair D, Tribus M, Kaindl R. Nanoindentation, High-Temperature Behavior, and Crystallographic/Spectroscopic Characterization of the High-Refractive-Index Materials TiTa2O7 and TiNb2O7. Inorg Chem 2015; 54:6836-48. [DOI: 10.1021/acs.inorgchem.5b00733] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Lukas Perfler
- Institute
of Mineralogy and Petrography, University of Innsbruck, Innrain
52f, 6020 Innsbruck, Austria
| | - Volker Kahlenberg
- Institute
of Mineralogy and Petrography, University of Innsbruck, Innrain
52f, 6020 Innsbruck, Austria
| | - Christoph Wikete
- Institute for Structural Engineering and
Material Sciences, Material Technology Innsbruck, University of Innsbruck, Technikerstr. 11/19a, 6020 Innsbruck, Austria
| | - Daniela Schmidmair
- Institute
of Mineralogy and Petrography, University of Innsbruck, Innrain
52f, 6020 Innsbruck, Austria
| | - Martina Tribus
- Institute
of Mineralogy and Petrography, University of Innsbruck, Innrain
52f, 6020 Innsbruck, Austria
| | - Reinhard Kaindl
- Materials−Institute
for Surface Technologies and Photonics, Functional Surfaces, JOANNEUM RESEARCH Forschungsgesellschaft mbH, Leobner Straße 94, 8712 Niklasdorf, Austria
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15
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Batuk M, Turner S, Abakumov AM, Batuk D, Hadermann J, Van Tendeloo G. Atomic structure of defects in anion-deficient perovskite-based ferrites with a crystallographic shear structure. Inorg Chem 2014; 53:2171-80. [PMID: 24479580 DOI: 10.1021/ic4028404] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Crystallographic shear (CS) planes provide a new structure-generation mechanism in the anion-deficient perovskites containing lone-pair cations. Pb2Sr2Bi2Fe6O16, a new n = 6 representative of the A(n)B(n)O(3n-2) homologous series of the perovskite-based ferrites with the CS structure, has been synthesized using the solid-state technique. The structure is built of perovskite blocks with a thickness of four FeO6 octahedra spaced by double columns of FeO5 edge-sharing distorted tetragonal pyramids, forming 1/2[110](101)p CS planes (space group Pnma, a = 5.6690(2) Å, b = 3.9108(1) Å, c = 32.643(1) Å). Pb2Sr2Bi2Fe6O16 features a wealth of microstructural phenomena caused by the flexibility of the CS planes due to the variable ratio and length of the constituting fragments with {101}p and {001}p orientation. This leads to the formation of "waves", "hairpins", "Γ-shaped" defects, and inclusions of the hitherto unknown layered anion-deficient perovskites Bi2(Sr,Pb)Fe3O8.5 and Bi3(Sr,Pb)Fe4O11.5. Using a combination of diffraction, imaging, and spectroscopic transmission electron microscopy techniques this complex microstructure was fully characterized, including direct determination of positions, chemical composition, and coordination number of individual atomic species. The complex defect structure makes these perovskites particularly similar to the CS structures in ReO3-type oxides. The flexibility of the CS planes appears to be a specific feature of the Sr-based system, related to the geometric match between the SrO perovskite layers and the {100}p segments of the CS planes.
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Affiliation(s)
- Maria Batuk
- Electron Microscopy for Materials Research (EMAT), University of Antwerp , Groenenborgerlaan 171, B-2020 Antwerp, Belgium
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16
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Lee CH, Orloff ND, Birol T, Zhu Y, Goian V, Rocas E, Haislmaier R, Vlahos E, Mundy JA, Kourkoutis LF, Nie Y, Biegalski MD, Zhang J, Bernhagen M, Benedek NA, Kim Y, Brock JD, Uecker R, Xi XX, Gopalan V, Nuzhnyy D, Kamba S, Muller DA, Takeuchi I, Booth JC, Fennie CJ, Schlom DG. Exploiting dimensionality and defect mitigation to create tunable microwave dielectrics. Nature 2013; 502:532-6. [PMID: 24132232 DOI: 10.1038/nature12582] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Accepted: 08/19/2013] [Indexed: 11/09/2022]
Abstract
The miniaturization and integration of frequency-agile microwave circuits--relevant to electronically tunable filters, antennas, resonators and phase shifters--with microelectronics offers tantalizing device possibilities, yet requires thin films whose dielectric constant at gigahertz frequencies can be tuned by applying a quasi-static electric field. Appropriate systems such as BaxSr1-xTiO3 have a paraelectric-ferroelectric transition just below ambient temperature, providing high tunability. Unfortunately, such films suffer significant losses arising from defects. Recognizing that progress is stymied by dielectric loss, we start with a system with exceptionally low loss--Srn+1TinO3n+1 phases--in which (SrO)2 crystallographic shear planes provide an alternative to the formation of point defects for accommodating non-stoichiometry. Here we report the experimental realization of a highly tunable ground state arising from the emergence of a local ferroelectric instability in biaxially strained Srn+1TinO3n+1 phases with n ≥ 3 at frequencies up to 125 GHz. In contrast to traditional methods of modifying ferroelectrics-doping or strain-in this unique system an increase in the separation between the (SrO)2 planes, which can be achieved by changing n, bolsters the local ferroelectric instability. This new control parameter, n, can be exploited to achieve a figure of merit at room temperature that rivals all known tunable microwave dielectrics.
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Affiliation(s)
- Che-Hui Lee
- 1] Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA [2] Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA [3]
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17
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Jeong J, Aetukuri N, Graf T, Schladt TD, Samant MG, Parkin SSP. Suppression of metal-insulator transition in VO2 by electric field-induced oxygen vacancy formation. Science 2013; 339:1402-5. [PMID: 23520104 DOI: 10.1126/science.1230512] [Citation(s) in RCA: 356] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Electrolyte gating with ionic liquids is a powerful tool for inducing novel conducting phases in correlated insulators. An archetypal correlated material is vanadium dioxide (VO(2)), which is insulating only at temperatures below a characteristic phase transition temperature. We show that electrolyte gating of epitaxial thin films of VO(2) suppresses the metal-to-insulator transition and stabilizes the metallic phase to temperatures below 5 kelvin, even after the ionic liquid is completely removed. We found that electrolyte gating of VO(2) leads not to electrostatically induced carriers but instead to the electric field-induced creation of oxygen vacancies, with consequent migration of oxygen from the oxide film into the ionic liquid. This mechanism should be taken into account in the interpretation of ionic liquid gating experiments.
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Affiliation(s)
- Jaewoo Jeong
- IBM Almaden Research Center, San Jose, CA 95120, USA
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18
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Batuk D, Hadermann J, Abakumov A, Vranken T, Hardy A, Van Bael M, Van Tendeloo G. Layered Perovskite-Like Pb2Fe2O5 Structure as a Parent Matrix for the Nucleation and Growth of Crystallographic Shear Planes. Inorg Chem 2011; 50:4978-86. [DOI: 10.1021/ic200211x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Dmitry Batuk
- EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
| | - Joke Hadermann
- EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
| | - Artem Abakumov
- EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
| | - Thomas Vranken
- Institute for Materials Research, Inorganic and Physical Chemistry, Hasselt University, Agoralaan Building D, 3590 Diepenbeek, Belgium
| | - An Hardy
- Institute for Materials Research, Inorganic and Physical Chemistry, Hasselt University, Agoralaan Building D, 3590 Diepenbeek, Belgium
- Division IMOMEC, IMEC, Agoralaan Building D, 3590 Diepenbeek, Belgium
| | - Marlies Van Bael
- Institute for Materials Research, Inorganic and Physical Chemistry, Hasselt University, Agoralaan Building D, 3590 Diepenbeek, Belgium
- Division IMOMEC, IMEC, Agoralaan Building D, 3590 Diepenbeek, Belgium
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19
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Reeswinkel T, Music D, Schneider JM. Coulomb-potential-dependent decohesion of Magnéli phases. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:292203. [PMID: 21399296 DOI: 10.1088/0953-8984/22/29/292203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Transition metal oxide Magnéli phases are traditionally described as crystallographic shear structures. Some of these phases feature a layered crystal structure based on deformed metal-oxygen octahedra. Here, we describe the correlation between structure, decohesion energies and elastic properties of WO(3), ReO(3), MoO(2), VO(2), V(2)O(5) and TiO(2) using ab initio calculations. Decohesion energies and elastic constants C(44) are inversely proportional to the original distance between the cleaved layers and correspond to the screened Coulomb potential. This can be understood based on the electronic structure. The bond strength decreases rapidly as the distance is increased, resulting in weak coupling between the layers, which in turn causes the formation of easily plastically deformable structures.
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20
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Mosset A, Lecante P, Galy J, Livage J. Structural analysis of amorphous V2O5 by large-angle X-ray scattering. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/13642818208246430] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Alain Mosset
- a Laboratoire de Chimie de Coordination du CNRS , 205 route de Narbonne, 31400 , Toulouse , France
| | - Pierre Lecante
- a Laboratoire de Chimie de Coordination du CNRS , 205 route de Narbonne, 31400 , Toulouse , France
| | - Jean Galy
- a Laboratoire de Chimie de Coordination du CNRS , 205 route de Narbonne, 31400 , Toulouse , France
| | - Jacques Livage
- b Université Pierre et Marie Curie , Spectrochimie du Solide, ERA 387 , 4place Jussieu, 75230 Paris, Cedex 05 , France
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21
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22
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Sayagués MJ, Krumeich F, Hutchison JL. Solid-gas reactions of complex oxides inside an environmental high-resolution transmission electron microscope. Micron 2001; 32:457-71. [PMID: 11163720 DOI: 10.1016/s0968-4328(00)00055-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In a gas reaction cell (GRC), installed in a high-resolution transmission electron microscope (HRTEM) (JEOL 4000EX), samples can be manipulated in an ambient atmosphere (p<50mbar). This experimental setup permits not only the observation of solid-gas reactions in situ at close to the atomic level but also the induction of structural modifications under the influence of a plasma, generated by the ionization of gas particles by an intense electron beam. Solid state reactions of non-stoichiometric niobium oxides and niobium tungsten oxides with different gases (O2, H2 and He) have been carried out inside this controlled environment transmission electron microscope (CETEM), and this has led to reaction products with novel structures which are not accessible by conventional solid state synthesis methods. Monoclinic and orthorhombic Nb(12)O(29) crystallize in block structures comprising [3x4] blocks. The oxidation of the monoclinic phase occurs via a three step mechanism: firstly, a lamellar defect of composition Nb(11)O(27) is formed. Empty rectangular channels in this defect provide the diffusion paths in the subsequent oxidation. In the second step, microdomains of the Nb(22)O(54) phase are generated as an intermediate state of the oxidation process. The structure of the final product Nb(10)O(25), which consists of [3x3] blocks and tetrahedral coordinated sites, is isostructural to PNb(9)O(25). Microdomains of this apparently metastable phase appear as a product of the Nb(22)O(54) oxidation. The oxidation reaction of Nb(12)O(29) was found to be a reversible process: the reduction of the oxidation product with H(2) results in the formation of the starting Nb(12)O(29) structure. On the other hand, the block structure of Nb(12)O(29) has been destroyed by a direct treatment of the sample with H(2) while NbO in a cubic rock salt structure is produced. This in situ technique has also been applied to niobium tungsten oxides which constitute the solid solution series Nb(8-n)W9(+n)O47 with 0< or =n< or =4. All of these phases crystallize in the threefold tetragonal tungsten bronze (TTB) superstructure of Nb(8)W(9)O(47) (n=0). In the main reaction, these phases decompose in a gas plasma (O2, H2 or He, p=20mbar) into WO(3-x), which evaporates and solidifies again near the irradiated crystallite, and (Nb,W)(24)O(64), which crystallizes in a 2a superstructure of the TTB type observed here for the first time in the system Nb-W-O. Nb(8)W(9)O(47), Nb(7)W(10)O(47) and Nb(6)W(11)O(47) always react in this way, independent of the applied gas. On the other hand, the treatment of Nb(5)W(12)O(47) (n=3) and Nb(4)W(13)O(47) (n=4) in an oxygen atmosphere often caused a different reaction: these phases have been oxidized and a heavily disordered bronze-type structure has been formed. The oxygen excess in these products is largely accommodated in segregated domains of WO(3).
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Affiliation(s)
- M J Sayagués
- Instituto de Ciencia de Materiales de Sevilla, C.S.I.C. c/ Américo Vespucio, s/n Isla de la Cartuja, 41092, Sevilla, Spain
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23
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Abstract
In homogeneous solid state reactions, transformation takes place within the crystals, and structural continuity is preserved; reactant and product structures are coherently intergrown. If the transformation starts independently at numerous loci, the incompletely reacted state of the crystals is inherently disordered. Crystallographic methods that average the structure over the whole crystal cannot fully characterize the actual, real-space structure, as it evolves during reaction, but that structure can, in favourable cases, be sampled by high resolution electron microscopy. Homogeneous reactions in the niobium oxide ‘block structure’ type crystals lend themselves to this technique. This study relates to the oxidation of the lower niobium oxides, Nb
22
O
54
, Nb
25
O
62
and Nb
53
O
132
, to niobium pentoxide. In each case, complete oxidation takes place at very low temperatures; the first products are reported to differ little in structure from the parent oxides, and to transform continuously into the stable polymorphic form,
H
-Nb
2
O
5
, over a wide temperature range and via several intermediate structures. By using lattice imaging methods, the structure elements present at each stage in the reactions have been identified, and their rearrangement has been followed. The initial oxidation step is completely non-reconstructive, and produces cation-deficient modifications of the original structures; all subsequent changes take place at constant composition, Nb
2
O
5
. In oxidized Nb
22
O
54
, a drastic rearrangement sets in at 350-400 °C, involving (
a
) an exchange of places and an apparent diffusion of the columnar structure elements (or blocks) and (
b
) a disproportionation that creates blocks of different cross sections. By a suitable mapping method, it is possible to infer exactly where, and how many, niobium atoms have undergone displacement into new sites, and to show that a single mechanism, proposed by Andersson and Wadsley, effects the observed changes of structure. Only a few atoms at a time, at the edge of one block, need to shift. Passing through a highly disordered state, blocks (3x3) octahedra in cross section are progressively segregated into microdomains of a new polymorphic structure of Nb
2
O
5
, Nb
10
O
25
, while blocks (5 x 3) octahedra in cross section are formed by disproportionation and built into microdomains of
H
-Nb
2
O
5
. These changes are initiated at random centres, 8-10 nm apart, starting at the edge of a single block; the displacements are propagated rapidly up the crystal
b
-axis and relatively slowly from block to block along rows and up files of blocks. Extended defects and compromise structures are formed where effects spreading from different initiating centres impinge; these faults serve as sinks for eliminating cation vacancies. The final result, stable up to 950 °C, is a domain structure, with nearly continuous walls of Nb
10
O
25
enclosing slabs of
H
-Nb
2
O
5
structure, and intersected by nearly continuous walls of fault structure. In oxidized Nb
25
O
62
, the first stage detected is the formation of triangular nuclei; one side of the triangle is formed of
H
-Nb
2
O
5
structure, the other side of Nb
10
O
25
structure, with an abrupt boundary to unchanged Nb
25
O
62
in each case. As these nuclei expand, by propagation of atom row displacements along rows and files of blocks, they merge to create relatively extensive domains of
H
-Nb
2
O
5
structure, separated by narrow walls of Nb
10
O
25
and linked by faults. Transformation of oxidized Nb
53
O
132
is similar. Long annealing of all the oxides at 900 °G gives products with essentially similar domain structures, but differing in the relative proportions of
H
-Nb
2
O
5
and Nb
10
O
25
domains. They are stable up to 950 °C; at higher temperatures, transformation into
H
-Nb
2
O
5
appears to be a catastrophic, and probably a heterogeneous process, for after heating at 950-1100 °C, any one crystal is either fully transformed into recrystallized
H
-Nb
2
O
5
or retains its domain structure with no significant change. There is some evidence that the domain structure is mobile at high temperatures.
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24
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Abstract
Calculations have been made of the energetics of reduced rutile (TiO
2
) crystals containing (
a
) an isolated {132} c. s. plane, (
b
) an ordered array of {132} c. s. planes corresponding to an oxide of composition Ti
20
O
39
, (
c
) a vacancy disc lying on {132} planes and (
d
) an ordered array of vacancy discs lying on {132} planes, which gives the crystal a composition of Ti
20
O
39
. The calculations were made by using the polarizable point ion shell model, and by taking the electronic polarizabilities of the ions involved into account. The results show that the c. s. planes are preferred to vacancy discs, and that this is largely due to the electronic polarization energy terms. The enthalpy of formation of an isolated {132} c. s. plane in rutile was calculated. A comparison with an estimate of the enthalpy of formation of the vacancy disc suggests that vacancy discs will be converted into c. s. planes in real crystals and will not exist as discrete defects. The change of the energy terms as the polarizabilities of the ions varied was also calculated to quantify the relation between preferred defect structure and dielectric constant. It was found that a change in dielectric constant did not have a significant effect upon the stability of vacancy discs, but did have a large effect on the energetics of c. s. planes, which suggests that c. s. planes are only favoured in crystals of high dielectric constant. It is shown that electronic polarizability is of importance in stabilizing {132} c. s. planes and that the polarizability of the O
2 ─
ions, in particular, is of great significance.
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25
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Precipitation phenomena in non-stoichiometric oxides I. Pairs of crystallographic shear planes in reduced rutiles. ACTA ACUST UNITED AC 1997. [DOI: 10.1098/rspa.1984.0017] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
High-resolution electron microscopy, in conjunction with controlled specimen preparation procedures, has enabled the nature and structure of the small defects existing within the nonstoichiometric phase TiO
2-x
(0 ≤ x ≤ 0.01) to be investigated. In particular, the precipitation of
pairs
of crystallographic shear planes (c. s. p.) and their subsequent separation has been observed. The atomic mechanisms involved in c. s. p. nucleation and growth and the eventual evolution to an ordered c. s. structure have been elucidated by using new linear cationic interstitial defect structural models. The results emphasize the decisive influence that cooling history has on the microstructures observed at room temperature and suggest that similar new phenomena will be discovered in observations of other non-stoichiometric chemical systems.
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Prinz G, Gruehn R. Beitr�ge zur Untersuchung anorganischer nichtst�chiometrischer Verbindungen. XLIV. Neue elektronenmikroskopische Untersuchung zur Realstruktur der metastabilen Nb2O5-Modifikation Ox1C. Z Anorg Allg Chem 1996. [DOI: 10.1002/zaac.19966220911] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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27
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Onishi H, Iwasawa Y. Dynamic visualization of a metal-oxide-surface/gas-phase reaction: Time-resolved observation by scanning tunneling microscopy at 800 K. PHYSICAL REVIEW LETTERS 1996; 76:791-794. [PMID: 10061551 DOI: 10.1103/physrevlett.76.791] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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28
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Onishi H, Fukui KI, Iwasawa Y. Atomic-Scale Surface Structures of TiO2(110) Determined by Scanning Tunneling Microscopy: A New Surface-Limited Phase of Titanium Oxide. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 1995. [DOI: 10.1246/bcsj.68.2447] [Citation(s) in RCA: 175] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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29
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Beitr�ge zur Untersuchung anorganischer nichtst�chiometrischer Verbindungen. XLIII. Darstellung und elektronenmikroskopische Untersuchung von (Cr, Nb)12O29. Z Anorg Allg Chem 1994. [DOI: 10.1002/zaac.19946200515] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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30
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31
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Eyring L, Dufner C, Goral J, Holladay A. High-resolution electron microscopic studies of chemical reactions in thin films. Ultramicroscopy 1985. [DOI: 10.1016/0304-3991(85)90142-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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32
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33
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Hirotsu Y, Tsunashima Y, Nagakura S, Kuwamoto H, Sato H. High-resolution electron microscopy of microsyntactic intergrowth in VnO2n−1. J SOLID STATE CHEM 1982. [DOI: 10.1016/0022-4596(82)90212-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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