Refinement of Phase Formation in the Na2MoO4-Hf(MoO4)2 System. Crystal Structure of the New Binary Molybdate Na8Hf(MoO4)6 |
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| Authors: | S F Solodovnikov B G Bazarov L V Balsanova Z A Solodovnikova and Zh G Bazarova |
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| Institution: | (1) A. V. Nikolaev Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia;(2) Baikal Insitute of Nature Management, Siberian Branch, Russian Academy of Sciences, Ulan-Ude, Russia;(3) Buryat State University, Ulan-Ude, Russia |
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| Abstract: | Phase equilibria in the subsolidus region of the Na2MoO4-Hf(MoO4)2 system have been investigated. The existence of Na2Hf(MoO4)3 was confirmed, and a new binary molybdate, Na8Hf(MoO4)6, has been found, whose crystal structure with dimensions a = 20.661(3) Å, b = 9.816(1) Å, c = 13.796(3) Å, β = 113.47(1)°, Z = 4, space group C2/c, R = 0.023 is similar to that of K8Hf(MoO4)6. In the structure, each HfO6 octahedron is linked (through common vertices) to six MoO4 tetrahedra, forming Hf(MoO4)6]8− cluster groups. Between the groups are Na+ ions having considerably distorted tetragonal pyramidal or octahedral oxygen surroundings; c.n. of sodium here is 5 or 6 versus c.n. = 7–9 of potassium in K8Hf(MoO4)6. The open irregular environment of sodium and the continuous three-dimensional openwork of oxygen polyhedra around sodium suggest that Na8Hf(MoO4)6 or its analogs may be good ion conductors.Original Russian Text Copyright © 2004 by S. F. Solodovnikov, B. G. Bazarov, L. V. Balsanova, Z. A. Solodovnikova, and Zh. G. Bazarova__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 1044–1048, November–December, 2004. |
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| Keywords: | sodium hafnium binary molybdates phase equilibria synthesis crystal structure ion conductivity |
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