Synthesis and crystal structures of new oxyapatites BiCa_4?xLa_x(VO₄)_3?x(GeO₄)_xO, x=1-3

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• 作者：V.D. Zhuravlev ; A.P. Tyutyunnik ; V.G. Zubkov ; L.A. Perelyaeva ; I.V. Baklanova ; A.L. Blinova
• 关键词：Germanate&ndash ; vanadates ; Oxyapatite ; Heterovalent substitution
• 刊名：Journal of Solid State Chemistry
• 出版年：2012
• 出版时间：October, 2012
• 年：2012
• 卷：194
• 期：Complete
• 页码：32-36
• 全文大小：389 K

文摘

New germanate-vanadates with the general formula BiCa_4?xLa_x(VO₄)_3?x(GeO₄)_xO, x=1?3, have been synthesized by the nitrate-citrate method and characterized. Structural refinement based on X-ray powder diffraction data showed that these compounds are isostructural with BiCa₄(VO₄)₃O (space group P6₃/m (N 176), Z=2, §Ñ=9.8327-9.8755(3), and §ã=7.1203-7.2133(2) ). They may be viewed as continuous series of solid solutions where Ca²⁺ and V⁵⁺ cations in the crystal lattice of vanadate BiCa₄(VO₄)₃O are replaced by La³⁺ and Ge⁴⁺ cations. In the process of substitution, the La³⁺ cations occupy mainly the 4f lattice sites of the germanate-vanadate oxyapatites, but the filling of the 4f and 6h lattice sites in the germanate BiCaLa₃(GeO₄)₃ is equivalent. IR and Raman spectra were studied. The Raman spectra clearly show a two-mode behavior: the lines of GeO₄ and VO₄ are separated from each other, and the (V/Ge)O₄ tetrahedra exhibit a quasi-independent behavior.