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Borges FH, Guidorzi MV, Labaki HDP, Ferreira RAS, Gonçalves RR. Refined structural studies on the fluorite-related polymorphs of sol-gel undoped and Eu 3+-doped yttrium tantalates. Dalton Trans 2024; 53:6020-6030. [PMID: 38470350 DOI: 10.1039/d4dt00338a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/13/2024]
Abstract
Compounds with the general formula RE3MO7 (RE = rare earth ions; M = Ta, Nb, Sb, Ru, Ir, Os, Re, etc.), crystallize as a fluorite-related structure, forming polymorphs with different space groups. The space group strongly depends on the RE3+ and M5+ ionic radii and processing conditions. Structural characterization is well-established for the lanthanide series, but literature studies have divergent views about how to attribute yttrium tantalate (Y3TaO7) space groups-some authors have described the Y3TaO7 structure as orthorhombic and belonging to space group C2221 or Ccmm, whereas others have assigned a cubic Fm3̄m structure to it. Here, we have characterized the structure of undoped and Eu3+-doped Y3TaO7 (0.1 to 50 mol% of Eu3+) samples synthesized by the sol-gel method that crystallized as a cubic disordered fluorite-type structure, space group Fm3̄m. Their powder X-ray diffraction measurements, Rietveld analyzes and Raman spectra were used as a conclusive technique of the structural properties. We have also investigated whether a secondary phase (M'-YTaO4) emerged in the samples and compared the phase composition of each sample to their Raman spectra. Low-temperature photoluminescence measurements (∼15 K) using Eu3+ as a structural probe helped us analyze the inhomogeneous broadening observed in the emission spectra. These measurements can be used as an important tool to attribute the crystalline phases of rare earth tantalates and niobates.
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Affiliation(s)
- Fernanda Hediger Borges
- Laboratório de Materiais Luminescentes Micro e Nanoestruturados - Mater Lumen, Departamento de Química, FFCLRP, Universidade de São Paulo, SP, Brazil.
| | - Maria Vitória Guidorzi
- Laboratório de Materiais Luminescentes Micro e Nanoestruturados - Mater Lumen, Departamento de Química, FFCLRP, Universidade de São Paulo, SP, Brazil.
| | - Hayra do Prado Labaki
- Laboratório de Materiais Luminescentes Micro e Nanoestruturados - Mater Lumen, Departamento de Química, FFCLRP, Universidade de São Paulo, SP, Brazil.
| | - Rute A S Ferreira
- Department of Physics and CICECO-Aveiro Institute of Materials, University of Aveiro, Aveiro, Portugal
| | - Rogéria Rocha Gonçalves
- Laboratório de Materiais Luminescentes Micro e Nanoestruturados - Mater Lumen, Departamento de Química, FFCLRP, Universidade de São Paulo, SP, Brazil.
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Gagarin PG, Guskov AV, Guskov VN, Nikiforova GE, Khoroshilov AV, Tyurin AV, Gavrichev KS. Sm3TaO7: Heat Capacity and Thermal Expansion. RUSS J INORG CHEM+ 2022. [DOI: 10.1134/s0036023622602070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Guskov AV, Gagarin PG, Guskov VN, Tyurin AV, Khoroshilov AV, Gavrichev KS. Thermodynamic Properties of Gadolinium Tantalate Gd3TaO7. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2022. [DOI: 10.1134/s0036024422060103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Subramani T, Voskanyan A, Jayanthi K, Abramchuk M, Navrotsky A. A Comparison of Order-Disorder in Several Families of Cubic Oxides. Front Chem 2021; 9:719169. [PMID: 34540800 PMCID: PMC8440809 DOI: 10.3389/fchem.2021.719169] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 08/02/2021] [Indexed: 11/23/2022] Open
Abstract
Order-disorder on both cation and oxygen sites is a hallmark of fluorite-derived structures, including pyrochlores. Ordering can occur on long- and short-range scales and can result in persistent metastable states. In various cubic oxide systems, different types of disorder are seen. The purpose of this paper is to review and compare the types and energetics of order-disorder phenomena in several families of cubic oxides having pyrochlore, weberite, defect fluorite, perovskite, rocksalt, and spinel structures. The goal is to better understand how structure, composition, and thermodynamic parameters (enthalpy and entropy) determine the feasibility of different competing ordering processes and structures in these diverse systems.
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Affiliation(s)
| | | | | | | | - A. Navrotsky
- School of Molecular Sciences and Navrotsky Eyring Center for Materials of the Universe, Arizona State University, Tempe, AZ, United States
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Shelyug A, Rafiuddin MR, Mesbah A, Clavier N, Szenknect S, Dacheux N, Guo X, Navrotsky A. Effect of Annealing on Structural and Thermodynamic Properties of ThSiO 4-ErPO 4 Xenotime Solid Solution. Inorg Chem 2021; 60:12020-12028. [PMID: 34328730 DOI: 10.1021/acs.inorgchem.1c01137] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The effect of annealing on structural and thermochemical properties of a thorite-xenotime solid solution Th1-xErx(SiO4)1-x(PO4)x was assessed. The samples synthesized at low temperatures and stored at room temperature for 2 years retained their tetragonal structures. This structure was also maintained after heating to 1100 °C. During annealing, the structure lost water and exsolved some thorianite phases. The thermodynamic parameters did not change much after annealing, suggesting that xenotime was not a low-temperature metastable phase but rather a stable structure able to withstand elevated temperatures regardless of the thorium content. The solid solution exhibited subregular behavior with the Margules function W(x) = (73.1 ± 20.1) - (125.7 ± 49.8)·x.
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Affiliation(s)
- Anna Shelyug
- Institute of Solid State Chemistry, Yekaterinburg 620990, Russia
| | | | - Adel Mesbah
- ICSM, Univ Montpellier, CNRS, CEA, ENSCM, Site de Marcoule, Bagnols-sur-Cèze 30207, France.,Institut de Recherches sur la Catalyse et l'Environnement de Lyon, IRCELYON, UMR5256, CNRS, Univ Lyon, Université Lyon 1, 2 Avenue Albert Einstein, Villeurbanne Cedex 69626, France
| | - Nicolas Clavier
- ICSM, Univ Montpellier, CNRS, CEA, ENSCM, Site de Marcoule, Bagnols-sur-Cèze 30207, France
| | - Stéphanie Szenknect
- ICSM, Univ Montpellier, CNRS, CEA, ENSCM, Site de Marcoule, Bagnols-sur-Cèze 30207, France
| | - Nicolas Dacheux
- ICSM, Univ Montpellier, CNRS, CEA, ENSCM, Site de Marcoule, Bagnols-sur-Cèze 30207, France
| | - Xiaofeng Guo
- Department of Chemistry and Alexandra Navrotsky Institute for Experimental Thermodynamics, Washington State University, Pullman, Washington 99164, United States
| | - Alexandra Navrotsky
- School of Molecular Sciences a Center for Materials of the Universe, Arizona State University, Tempe, Arizona 85287, United States
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Drey DL, O'Quinn EC, Subramani T, Lilova K, Baldinozzi G, Gussev IM, Fuentes AF, Neuefeind JC, Everett M, Sprouster D, Navrotsky A, Ewing RC, Lang M. Disorder in Ho 2Ti 2-x Zr x O 7: pyrochlore to defect fluorite solid solution series. RSC Adv 2020; 10:34632-34650. [PMID: 35514412 PMCID: PMC9056788 DOI: 10.1039/d0ra07118h] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 09/08/2020] [Indexed: 11/21/2022] Open
Abstract
Pyrochlore (A2B2O7) is an important, isometric structure-type because of its large variety of compositions and structural derivatives that are generally related to different disordering mechanisms at various spatial scales. The disordering is key to understanding variations in properties, such as magnetic behavior or ionic conduction. Neutron and X-ray total scattering methods were used to investigate the degree of structural disorder in the Ho2Ti2-x Zr x O7 (x = 0.0-2.0, Δx = 0.25) solid solution series as a function of the Zr-content, x. Ordered pyrochlores (Fd3̄m) disorder to defect fluorite (Fm3̄m) via cation and anion disordering. Total scattering experiments with sensitivity to the cation and anion sublattices provide unique insight into the underlying atomic processes. Using simultaneous Rietveld refinement (long-range structure) and small-box refinement PDF analysis (short-range structure), we show that the series undergoes a rapid transformation from pyrochlore to defect fluorite at x ≈ 1.2, while the short-range structure exhibits a linear increase in a local weberite-type phase, C2221, over the entire composition range. Enthalpies of formation from the oxides determined using high temperature oxide melt solution calorimetry support the structural data and provide insight into the effect of local ordering on the energetics of disorder. The measured enthalpies of mixing are negative and are fit by a regular solution parameter of W = -31.8 ± 3.7 kJ mol-1. However, the extensive short-range ordering determined from the structural analysis strongly suggests that the entropies of mixing must be far less positive than implied by the random mixing of a regular solution. We propose a local disordering scheme involving the pyrochlore 48f to 8a site oxygen Frenkel defect that creates 7-coordinated Zr sites contained within local weberite-type coherent nanodomains. Thus, the solid solution is best described as a mixture of two phases, with the weberite-type nanodomains triggering the long-range structural transformation to defect fluorite after accumulation above a critical concentration (50% Ti replaced by Zr).
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Affiliation(s)
- Devon L Drey
- Department of Nuclear Engineering, University of Tennessee Knoxville TN 37996 USA
| | - Eric C O'Quinn
- Department of Nuclear Engineering, University of Tennessee Knoxville TN 37996 USA
| | - Tamilarasan Subramani
- School of Molecular Sciences, Center for Materials of the Universe, Arizona State University Tempe AZ 85287 USA
| | - Kristina Lilova
- School of Molecular Sciences, Center for Materials of the Universe, Arizona State University Tempe AZ 85287 USA
| | - Gianguido Baldinozzi
- Laboratoire Structures, Propriétés et Modélisation des Solides, CNRS, Centrale Supélec, Université Paris-Saclay F-91190 Gif-sur-Yvette France
| | - Igor M Gussev
- Department of Nuclear Engineering, University of Tennessee Knoxville TN 37996 USA
| | | | - Joerg C Neuefeind
- Neutron Scattering Division, Oak Ridge National Laboratory Oak Ridge TN 37831 USA
| | - Michelle Everett
- Neutron Scattering Division, Oak Ridge National Laboratory Oak Ridge TN 37831 USA
| | - David Sprouster
- Department of Materials Science and Chemical Engineering, State University of New York Stony Brook NY 11794 USA
| | - Alexandra Navrotsky
- School of Molecular Sciences, Center for Materials of the Universe, Arizona State University Tempe AZ 85287 USA
| | - Rodney C Ewing
- Department of Geological Sciences, Stanford University Stanford CA 94305 USA
| | - Maik Lang
- Department of Nuclear Engineering, University of Tennessee Knoxville TN 37996 USA
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