Thermal expansion of Cr{sub 2x}Fe{sub 2-2x}Mo{sub 3}O{sub 12}, Al{sub 2x}Fe{sub 2-2x}Mo{sub 3}O{sub 12} and Al{sub 2x}Cr{sub 2-2x}Mo{sub 3}O{sub 12} solid solutions
- Departamento de Ciencia dos Materiais e Metalurgia, Pontificia Universidade Catolica de Rio de Janeiro-PUC-Rio, Rua Marques de Sao Vicente 225, Rio de Janeiro, RJ (Brazil)
- Laboratorio Nacional de Luz Sincrotron (LNLS), CP 6192, CEP 13083-970, Campinas, SP (Brazil)
The transition temperature from monoclinic to orthorhombic and the thermal expansion of the orthorhombic phase were investigated for three systems of the family A{sub 2}M{sub 3}O{sub 12}: Cr{sub 2x}Fe{sub 2-2x}Mo{sub 3}O{sub 12}, Al{sub 2x}Fe{sub 2-2x}Mo{sub 3}O{sub 12} and Al{sub 2x}Cr{sub 2-2x}Mo{sub 3}O{sub 12}. It was possible to obtain a single-phase solid solution in all studied samples (x=0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1). A linear relationship between the transition temperature and the fraction of A{sup 3+} cations (x) was observed for each system. In all orthorhombic solid solutions studied here the observed thermal expansion was anisotropic. These anisotropic thermal expansion properties of crystallographic axes a, b and c result in a low positive or near-zero overall linear coefficient of thermal expansion ({alpha}{sub l}={alpha}{sub V}/3). The relationship between the size of A{sup 3+} cations in A{sub 2}M{sub 3}O{sub 12} and the coefficient of thermal expansion is discussed. Near-zero thermal expansion of Cr{sub 2}Mo{sub 3}O{sub 12} is explained by the behavior of Cr-O and Mo-O bond distances, Cr-Mo non-bond distances and Cr-O-Mo bond angles with increasing temperature, estimated by Rietveld analysis of synchrotron X-ray powder diffraction data. - Graphical abstract: In this figure, all published overall linear coefficients of thermal expansion for orthorhombic A{sub 2}M{sub 3}O{sub 12} family obtained through diffraction methods as a function of A{sup 3+} cation radii size, together with dilatometric results, are plotted. Our results indicate that Cr{sub 2}Mo{sub 3}O{sub 12} does not exactly follow the established relationship.
- OSTI ID:
- 21128334
- Journal Information:
- Journal of Solid State Chemistry, Vol. 181, Issue 6; Other Information: DOI: 10.1016/j.jssc.2008.03.015; PII: S0022-4596(08)00142-4; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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