Disordered modifications of cobalt molybdate |
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Authors: | J. Chojnacki R. Kozłowski |
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Affiliation: | Department of Crystal Chemistry and Crystal Physics, Jagiellonian University, Cracow, Poland |
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Abstract: | The structures of recently discovered new high-temperature modifications of cobalt molybdate, a′-and a″-CoMoO4, were determined. a′-and a″-CoMoO4 appear after the phase a-CoMoO4 is heated above the temperature range 700–1000°C. They seem to be the disordered modifications of a-CoMoO4 with metal atoms distributed at random in an a-CoMoO4 oxygen network.The F(hkl) values, calculated for variously disordered a-CoMoO4 structure, were compared with the observed intensities of diffraction lines changing in the course of a → a′ and a → a″ transitions. It was concluded that a″-CoMoO44 has a completely disordered structure with random distribution of both Co and Mo atoms in oxygen interatomic voids. The a′-CoMoO4 is a partly disordered modification, with random distribution of some cations only.The temperature and the kind of order-disorder transition depend on the method of preparation of a-CoMoO4 samples.The disordered modifications of cobalt molybdate may be supercooled—even to room temperature—before it transforms rapidly into low-temperature b-CoMoO4 form. |
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Keywords: | Author to whom correspondence should be addressed. |
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