Preparation and structure of fluorite-type (Sr,Y)Cl2.05 |
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Authors: | Eileen Mason Harry A. Eick |
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Affiliation: | Department of Chemistry, Michigan State University, East Lansing, Michigan 48824 USA |
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Abstract: | Anion excess colorless fluorite-type strontium-yttrium chloride has been prepared. Single crystals of the SrY compound exhibit a primitive cubic lattice with a = 6.967(1)Å. Two mutually exclusive structural models for solutions, neither of which is exact, are discussed. The first is a vacancy model in which the extra charge which results from substitution of Y3+ for Sr2+ is balanced by the simultaneous removal of a Sr2+Cl? ion pair. This model requires individual ion sites to be partially occupied and nonequivalent and is strongly suggestive of vacancy ordering. Refinement in space group P1, with sites refined independenty, led to R = 0.1096. The second model describes the structure in terms of a Willis cluster of defects and includes both anion vacancies and interstitial anions. Full-matrix least squares refinement in space group Fm3m, with positions analogous to those in UO2.12 and (Ca,Y)F2.10, converged at R = 0.0633 for the 114 face-centered parent structure reflections whose |F|;2 > σ(F2). This second model is discussed in relation to a probable true solution which involves longrange order. |
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Keywords: | To whom correspondence should be addressed. |
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