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Versatility of Tellurium in Heteroanionic Ln 2O 2Te (Ln = La, Ce, Pr) and Tellurate Ln 2TeO 6 (Ln = La, Pr). Inorg Chem 2022; 61:18002-18009. [DOI: 10.1021/acs.inorgchem.2c02287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Vacancy-Driven Disorder and Elevated Dielectric Response in the Pyrochlore Pb 1.5Nb 2O 6.5. Inorg Chem 2022; 61:18601-18610. [DOI: 10.1021/acs.inorgchem.2c03031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Structural Diversity of Rare-Earth Oxychalcogenides. ACS OMEGA 2022; 7:8209-8218. [PMID: 35309485 PMCID: PMC8928505 DOI: 10.1021/acsomega.2c00186] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Accepted: 02/21/2022] [Indexed: 06/14/2023]
Abstract
Mixed-anion systems have garnered much attention in the past decade with attractive properties for diverse applications such as energy conversion, electronics, and catalysis. The discovery of new materials through mixed-cation and single-anion systems proved highly successful in the previous century, but solid-state chemists are now embracing an exciting design opportunity by incorporating multiple anions in compounds such as oxychalcogenides. Materials containing rare-earth ions are arguably a cornerstone of modern technology, and herein, we review recent advances in rare-earth oxychalcogenides. We discuss ternary rare-earth oxychalcogenides whose layered structures illustrate the characters and bonding preferences of oxide and chalcogenide anions. We then review quaternary compounds which combine anionic and cationic design strategies toward materials discovery and describe their structural diversity. Finally, we emphasize the progression from layered two-dimensional compounds to three-dimensional networks and the unique synthetic approaches which enable this advancement.
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Arc Synthesis, Crystal Structure, and Photoelectrochemistry of Copper(I) Tungstate. ACS APPLIED MATERIALS & INTERFACES 2021; 13:32865-32875. [PMID: 34251184 PMCID: PMC8311641 DOI: 10.1021/acsami.1c03928] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 06/25/2021] [Indexed: 06/13/2023]
Abstract
A little-studied p-type ternary oxide semiconductor, copper(I) tungstate (Cu2WO4), was assessed by a combined theoretical/experimental approach. A detailed computational study was performed to solve the long-standing debate on the space group of Cu2WO4, which was determined to be triclinic P1. Cu2WO4 was synthesized by a time-efficient, arc-melting method, and the crystalline reddish particulate product showed broad-band absorption in the UV-visible spectral region, thermal stability up to ∼260 °C, and cathodic photoelectrochemical activity. Controlled thermal oxidation of copper from the Cu(I) to Cu(II) oxidation state showed that the crystal lattice could accommodate Cu2+ cations up to ∼260 °C, beyond which the compound was converted to CuO and CuWO4. This process was monitored by powder X-ray diffraction and X-ray photoelectron spectroscopy. The electronic band structure of Cu2WO4 was contrasted with that of the Cu(II) counterpart, CuWO4 using spin-polarized density functional theory (DFT). Finally, the compound Cu2WO4 was determined to have a high-lying (negative potential) conduction band edge underlining its promise for driving energetic photoredox reactions.
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Role of f Electrons in the Optical and Photoelectrochemical Behavior of Ca(La 1- xCe x) 2S 4 (0 ≤ x ≤ 1). Inorg Chem 2019; 58:4553-4560. [PMID: 30888802 DOI: 10.1021/acs.inorgchem.9b00062] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This study focuses on a solid solution series, Ca(La1- xCe x)2S4 (0 ≤ x ≤ 1), where the f electron density is absent in CaLa2S4 and is progressively increased until it is maximized in CaCe2S4. Correspondingly, these samples, synthesized by a sealed ampule method, showed progressive variations in color ranging from gray for CaLa2S4 to orange-red for CaCe2S4. The crystal structural nuances of both the end members and three solid solutions with x = 0.25, 0.50, and 0.75 were established with the complementary use of synchrotron X-ray diffraction and neutron scattering. Interestingly, these data were consistent with a two-phase composition centered around each nominal solid solution stoichiometry. Optical characterization via diffuse reflectance spectroscopy and Tauc analyses showed a shrinking of the energy band gap (from the UV to vis range) when Ce was progressively introduced into the host CaLa2S4 structure. These data were in concert with electronic band structure calculations, using density functional theory, which showed the progressive formation of an intermediate f band when Ce was introduced intro the structure. Photoelectrochemical measurements in an aqueous redox electrolyte, as well as surface photovoltage and Kelvin probe measurements, revealed all samples to be n-type semiconductors. The valence and conduction band edge positions of the end members and the three solid solutions could be mapped, on both the redox and vacuum reference energy scales, by combining these measurements with the optical data.
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One-dimensional tellurium chains: Crystal structure and thermodynamic properties of PrCuxTe2 (x ~ 0.45). J SOLID STATE CHEM 2019. [DOI: 10.1016/j.jssc.2018.10.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Silver Oxide-Based Semiconductors for Solar Fuels Production and Environmental Remediation: a Solid-State Chemistry Approach. ChemElectroChem 2018. [DOI: 10.1002/celc.201800885] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Combining crystallography and complementary techniques to understanding small structural changes in intermetallic compounds and sulfides. Acta Crystallogr A Found Adv 2017. [DOI: 10.1107/s0108767317098075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Challenges in intermetallics: synthesis, structural characterization, and transitions. Dalton Trans 2012; 41:14225-35. [PMID: 22986914 DOI: 10.1039/c2dt31328f] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Intermetallics that contain rare-earth elements are particularly interesting because of their temperature- and pressure-dependent structural and physical transitions that make them potential candidates for magnetic applications. This article highlights synthetic routes and structural characterization advancements used to investigate intermetallic materials. Experimental and theoretical examples of three intermetallic structure types--ThCr(2)Si(2), Heusler and Laves--are discussed to present a historical review and to illustrate the grand challenges in unravelling structure-property relationships of intermetallic compounds.
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Structures and phase transitions of CePd3+xGa8-x: new variants of the BaHg11 structure type. J Am Chem Soc 2012; 134:12998-3009. [PMID: 22849326 DOI: 10.1021/ja302812s] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
New distorted variants of the cubic BaHg11 structure type have been synthesized in Ga flux. Multiple phases of CePd3+xGa8-x, which include an orthorhombic Pmmn structure (x = 3.21(2)), a rhombohedral R3m structure (x = 3.13(4)), and a cubic Fm3m superstructure (x = 2.69(6)), form preferentially depending on reaction cooling rate and isolation temperature. Differential thermal analysis and in situ temperature-dependent powder X-ray diffraction patterns show a reversible phase transition at approximately 640 °C between the low temperature orthorhombic and rhombohedral structures and the high temperature cubic superstructure. Single crystal X-ray diffraction experiments indicate that the general structure of BaHg11, including the intersecting planes of a kagomé-type arrangement of Ce atoms, is only slightly distorted in the low temperature phases. A combination of Kondo, crystal electric field, and magnetic frustration effects may be present, resulting in low temperature anomalies in magnetic susceptibility, electrical resistivity, and heat capacity measurements. In addition to CePd3+xGa8-x, the rare earth analogues REPd3+xGa8-x, RE = La, Nd, Sm, Tm, and Yb, were successfully synthesized and also crystallize in one of the lower symmetry space groups.
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Structure and properties of rhombohedral CePd3Ga8: A variant of the cubic parent compound with BaHg11 structure type. J SOLID STATE CHEM 2011. [DOI: 10.1016/j.jssc.2011.10.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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CsTe2O6–x: Novel Mixed-Valence Tellurium Oxides with Framework-Deficient Pyrochlore-Related Structure. Inorg Chem 2011; 50:8494-501. [DOI: 10.1021/ic2010375] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Discovery of the Griffiths phase in the itinerant magnetic semiconductor Fe1-xCoxS2. PHYSICAL REVIEW LETTERS 2008; 100:017209. [PMID: 18232818 DOI: 10.1103/physrevlett.100.017209] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Indexed: 05/25/2023]
Abstract
Critical points that can be suppressed to zero temperature are interesting because quantum fluctuations have been shown to dramatically alter electron gas properties. Here, the metal formed by Co doping the paramagnetic insulator FeS2, Fe1-xCoxS2 is demonstrated to order ferromagnetically at x > xc = 0.01+/-0.005, where we observe unusual transport, magnetic, and thermodynamic properties. We show that this magnetic semiconductor undergoes a percolative magnetic transition with distinct similarities to the Griffiths phase, including singular behavior at xc and zero temperature.
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Spin disorder and order in quasi-2D triangular Heisenberg antiferromagnets: comparative study of FeGa2S4, Fe2Ga2S5, and NiGa2S4. PHYSICAL REVIEW LETTERS 2007; 99:157203. [PMID: 17995208 DOI: 10.1103/physrevlett.99.157203] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2007] [Revised: 07/11/2007] [Indexed: 05/25/2023]
Abstract
Our single crystal study reveals that the single-layer S=2 triangular Heisenberg antiferromagnet FeGa2S4 forms a frozen spin-disordered state, similar to the S=1 isostructural magnet NiGa2S4. In this state, the magnetic specific heat C{M} is not only insensitive to the field, but shows a T2 dependence that scales to C{M} of NiGa2S4, suggesting the same underlying mechanism of the 2D coherent behavior. In contrast, the bilayer system Fe2Ga2S5 exhibits a 3D antiferromagnetic order.
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Rare Beryllium Icosahedra in the Intermediate Valence Compound CeBe 13 [ J. Am. Chem. Soc. 2004, 126, 13926−13927]. J Am Chem Soc 2006. [DOI: 10.1021/ja043190c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Metallic spin-liquid behavior of the geometrically frustrated Kondo lattice. PHYSICAL REVIEW LETTERS 2006; 96:087204. [PMID: 16606220 DOI: 10.1103/physrevlett.96.087204] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2005] [Indexed: 05/08/2023]
Abstract
Strongly frustrated magnetism of the metallic pyrochlore oxide Pr2Ir2O7 has been revealed by single crystal study. While Pr 4f moments have an antiferromagnetic RKKY interaction energy scale of /T*/ = 20 K mediated by Ir 5d-conduction electrons, no magnetic long-range order is found except for partial spin freezing at 120 mK. Instead, the Kondo effect, including a lnT dependence in the resistivity, emerges and leads to a partial screening of the moments below /T*/. Our results indicate that the underscreened moments show spin-liquid behavior below a renormalized correlation scale of 1.7 K.
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A comparison of the structure and localized magnetism in Ce2PdGa12 with the heavy fermion CePdGa6. J SOLID STATE CHEM 2005. [DOI: 10.1016/j.jssc.2005.09.013] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Crystal growth, characterization and physical properties of PrNiSb3, NdNiSb3 and SmNiSb3. J SOLID STATE CHEM 2004. [DOI: 10.1016/j.jssc.2004.08.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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4f-electron localization in CexLa 1-xM In5 with M=Co, Rh, or Ir. PHYSICAL REVIEW LETTERS 2004; 93:186405. [PMID: 15525189 DOI: 10.1103/physrevlett.93.186405] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2004] [Indexed: 05/24/2023]
Abstract
de Haas-van Alphen measurements on Ce(x)La(1-x)MIn(5) yield contrasting types of behavior that depend on whether M=Co and Ir or M=Rh. A stronger x-dependent scattering in the case of M=Co and Ir is suggestive of a stronger relative coupling, J/W, of the conduction electrons to the 4f electrons, which would then account for the development of a heavy composite Fermi-liquid state as x-->1. The failure of a composite Fermi-liquid state to form for any x in the case of M= Rh is shown to be inconsistent with theoretical models that propose antiferromagnetism to result from spin-density-wave formation.
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Abstract
Single-crystal X-ray diffraction experiments show that the Be atoms in CeBe13 form a Be12 icosahedra, which is a very unusual structural feature due, in part, to the remarkably low valence electron count of Be. Magnetization studies show that CeBe13 displays intermediate valence behavior, in which valence fluctuations between the Ce 4f0 and 4f1 states give rise to enhanced electronic specific heat and magnetic susceptibility. Calculations using ab initio theory were used to determine the electronic structure and bonding and to give insight into the relationship between the crystal structure, the bonding, and the intermediate valence behavior of CeBe13. The hybridization between the localized f electrons and the conduction electrons is responsible for the large values of the electronic specific heat coefficient (gamma approximately 100 mJ/mol K2) and magnetic susceptibility (chi approximately 1 x 10-3 emu/mol), which is in marked contrast to those of ordinary metals that have gamma approximately 1 mJ/mol K2 and chi approximately 1 x 10-5 emu/mol values. The magnetic susceptibility, chi = M/H versus T, of a single crystal of CeBe13 exhibits a broad maximum at Tmax approximately 130 K and is typical of intermediate valence systems with an unusually large energy scale (Kondo), TK approximately 500 K.
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Abstract
Single crystals of a new ternary compound, SmPd(2)Ga(2), have been synthesized by flux growth methods. This compound adopts a tetragonal space group I4/mmm, Z = 2, with lattice parameters a = 4.2170(3) A and c = 10.4140(3) A. The crystal structure is composed of layers of isolated Sm atoms and layers of PdGa(4) edge-sharing tetrahedra alternating along the c-axis. The sample is metallic (d rho/dT > 0) with a weak temperature dependence above 100 K. This new material has physical properties similar to those of other Sm intermetallics and has, most notably, a large positive magnetoresistance at low temperatures. Magnetic measurements indicate that SmPd(2)Ga(2) is ferromagnetic with T(c) approximately 5 K.
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