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Title: Structures and phase diagram for the system CaTiO{sub 3}-La{sub 2/3}TiO{sub 3}

Abstract

High-resolution neutron and synchrotron X-ray powder diffraction have been used to examine various compositions across the system (1-x)CaTiO{sub 3}-xLa{sub 2/3}TiO{sub 3}. The structures at room temperature were determined according to composition: in Pbnm for 0{<=}x{<=}0.5, Ibmm for 0.5<x<0.7, then I4/mcm for 0.7{<=}x<0.9, and finally in Cmmm for x{>=}0.9. Although the four structures are the same as those proposed previously in an X-ray diffraction study, the phase boundaries are somewhat different, in particular the Pbnm{r_reversible}Ibmm phase boundary has been extended from x{<=}0.4 to x>0.5 in the current study based on our high-resolution neutron diffraction data. From in situ measurements to identify structures above room temperature, an approximate composition-temperature phase diagram has been constructed, involving four temperature-induced phase transitions: Pbnm{sup {yields}}I4/mcm, Ibmm{sup {yields}}I4/mcm, I4/mcm{sup {yields}}Pm3-barm and Cmmm{sup {yields}}P4/mmm. - Graphical abstract: Phase diagram for Ca{sub (1-x)}La{sub 3x/2}TiO{sub 3} based on transition temperatures obtained from in situ neutron and synchrotron X-ray powder diffraction studies: depending on whether or not we have in-phase and/or out-of-phase octahedral tilting, whether we have long-range cation/vacancy ordering (the degree of ordering is indicated by shading), six distinct structures occur.

Authors:
 [1];  [2];  [3];  [2];  [4];  [5];  [3];  [6]
  1. Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234 (Australia), E-mail: zhaoming.zhang@ansto.gov.au
  2. Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234 (Australia)
  3. (United Kingdom)
  4. ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX (United Kingdom)
  5. Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom)
  6. Japan Synchrotron Radiation Research Institute/SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan)
Publication Date:
OSTI Identifier:
21015750
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 180; Journal Issue: 3; Other Information: DOI: 10.1016/j.jssc.2007.01.005; PII: S0022-4596(07)00022-9; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CALCIUM COMPOUNDS; LANTHANUM COMPOUNDS; NEUTRON DIFFRACTION; ORTHORHOMBIC LATTICES; PEROVSKITES; PHASE DIAGRAMS; PHASE TRANSFORMATIONS; TEMPERATURE RANGE 0273-0400 K; TETRAGONAL LATTICES; TITANATES; TRANSITION TEMPERATURE; VACANCIES; X-RAY DIFFRACTION

Citation Formats

Zhang Zhaoming, Lumpkin, Gregory R., Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, Howard, Christopher J., Knight, Kevin S., Whittle, Karl R., Department of Engineering Materials, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, and Osaka, Keiichi. Structures and phase diagram for the system CaTiO{sub 3}-La{sub 2/3}TiO{sub 3}. United States: N. p., 2007. Web. doi:10.1016/j.jssc.2007.01.005.
Zhang Zhaoming, Lumpkin, Gregory R., Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, Howard, Christopher J., Knight, Kevin S., Whittle, Karl R., Department of Engineering Materials, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, & Osaka, Keiichi. Structures and phase diagram for the system CaTiO{sub 3}-La{sub 2/3}TiO{sub 3}. United States. doi:10.1016/j.jssc.2007.01.005.
Zhang Zhaoming, Lumpkin, Gregory R., Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, Howard, Christopher J., Knight, Kevin S., Whittle, Karl R., Department of Engineering Materials, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, and Osaka, Keiichi. Thu . "Structures and phase diagram for the system CaTiO{sub 3}-La{sub 2/3}TiO{sub 3}". United States. doi:10.1016/j.jssc.2007.01.005.
@article{osti_21015750,
title = {Structures and phase diagram for the system CaTiO{sub 3}-La{sub 2/3}TiO{sub 3}},
author = {Zhang Zhaoming and Lumpkin, Gregory R. and Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ and Howard, Christopher J. and Knight, Kevin S. and Whittle, Karl R. and Department of Engineering Materials, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD and Osaka, Keiichi},
abstractNote = {High-resolution neutron and synchrotron X-ray powder diffraction have been used to examine various compositions across the system (1-x)CaTiO{sub 3}-xLa{sub 2/3}TiO{sub 3}. The structures at room temperature were determined according to composition: in Pbnm for 0{<=}x{<=}0.5, Ibmm for 0.5<x<0.7, then I4/mcm for 0.7{<=}x<0.9, and finally in Cmmm for x{>=}0.9. Although the four structures are the same as those proposed previously in an X-ray diffraction study, the phase boundaries are somewhat different, in particular the Pbnm{r_reversible}Ibmm phase boundary has been extended from x{<=}0.4 to x>0.5 in the current study based on our high-resolution neutron diffraction data. From in situ measurements to identify structures above room temperature, an approximate composition-temperature phase diagram has been constructed, involving four temperature-induced phase transitions: Pbnm{sup {yields}}I4/mcm, Ibmm{sup {yields}}I4/mcm, I4/mcm{sup {yields}}Pm3-barm and Cmmm{sup {yields}}P4/mmm. - Graphical abstract: Phase diagram for Ca{sub (1-x)}La{sub 3x/2}TiO{sub 3} based on transition temperatures obtained from in situ neutron and synchrotron X-ray powder diffraction studies: depending on whether or not we have in-phase and/or out-of-phase octahedral tilting, whether we have long-range cation/vacancy ordering (the degree of ordering is indicated by shading), six distinct structures occur.},
doi = {10.1016/j.jssc.2007.01.005},
journal = {Journal of Solid State Chemistry},
number = 3,
volume = 180,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
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  • A description and structural study of four quaternary compounds is furnished: (LaO)/sub 4/Ga/sub 1,33/S/sub 4/ and ..cap alpha..-LaGaS/sub 2/O have sheet structures, formed by (LaO) sheets and gallium sulfide sheets. La/sub 3/GaS/sub 5/O has a ribbon structure, formed by (La/sub 2/O) ribbons inside a LaGaS/sub 5/ sulfide skeleton. In the three preceding compounds, oxygen is bound only to lanthanum, and gallium is bound only to sulfur. No such bond selectivity occurs in ..beta..-LaGaS/sub 2/O and La/sub 3,33/Ga/sub 6/S/sub 12/O/sub 2/. An interpretation of the structural characteristics of the Ga - (O,S) arrangements is presented in relation to the composition. Amore » partial description of the phase diagram (for O/O + S) < 0.50) is presented. The La/sub 2/O/sub 2/S-Ga/sub 2/S/sub 3/ system is quasi-binary. The La/sub 2/O/sub 3/-Ga/sub 2/S/sub 3/ system is a section in the ternary system, involving three-phase equilibria. A description of the eutectic valleys and of the ternary invariants is furnished. 23 references, 8 figures, 5 tables.« less
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