Isomorphous substitution of europium for strontium in the structure of synthetic hydroxovanadate

Polycrystalline strontium–europium hydroxovanadates Sr 10− x Eu x (VO 4) 6(OH) 2− x O x were synthesized and studied by X-ray powder diffraction, infrared absorption and diffuse-reflectance spectroscopies and also thermogravimetry. The single-phase region of isomorphous substitution of Eu for Sr in...

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Bibliographic Details
Published in:	Journal of solid state chemistry Vol. 181; no. 9; pp. 2386 - 2392
Main Authors:	Get’man, E.I., Yablochkova, N.V., Loboda, S.N., Prisedsky, V.V., Antonovich, V.P., Chivireva, N.A.
Format:	Journal Article
Language:	English
Published:	Amsterdam Elsevier Inc 01-09-2008 Elsevier
Subjects:	ABSORPTION Apatite APATITES BOND LENGTHS Condensed matter: structure, mechanical and thermal properties Cross-disciplinary physics: materials science; rheology EUROPIUM COMPOUNDS Exact sciences and technology Hydroxovanadate Inorganic compounds INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY Isomorphism Materials science Materials synthesis; materials processing Physics POLYCRYSTALS RE elements Single-phase region SPECTROSCOPY STRONTIUM COMPOUNDS Structural and spectroscopic characteristics Structure of solids and liquids; crystallography Structure of specific crystalline solids TEMPERATURE RANGE 1000-4000 K THERMAL GRAVIMETRIC ANALYSIS VANADATES WATER Water absorbent X-RAY DIFFRACTION Structural and spectroscopic characteristics Water absorbent Isomorphism Apatite Hydroxovanadate Single-phase region RE elements Rietveld method Infrared spectroscopy Polycrystals XRD High temperature Bond lengths Structure composition relationship Strontium Reflection spectrum Absorption spectra Strontium Europium Hydroxides Vanadates Europium Coordination bond Capillary condensation Diffuse reflection Thermogravimetry Vanadates Apatite structure
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Summary:	Polycrystalline strontium–europium hydroxovanadates Sr 10− x Eu x (VO 4) 6(OH) 2− x O x were synthesized and studied by X-ray powder diffraction, infrared absorption and diffuse-reflectance spectroscopies and also thermogravimetry. The single-phase region of isomorphous substitution of Eu for Sr in hydroxovanadate has been found to lie in the compositional interval 0⩽ x⩽0.18 at 800 °C. Refinement of X-ray diffraction (XRD) patterns by the Rietveld method shows that Eu substitutes for Sr preferentially at the Sr(1) sites of the apatite structure. The substitution results in a more uniform distribution of Sr–O bond lengths in coordination polyhedra both around Sr (1) and Sr (2) sites and also in a slight contraction of the vanadate anion VO 4 3−. Synthetic Sr hydroxovanadates absorb a considerable amount of water in two forms: capillary condensed and chemically combined. The latter form may be absorbed at temperatures as high as 500 °C. The results of this paper contribute to a general picture of substitution effects of the rare-earth (RE) elements in the apatite structure. The dependence of the substitution limit x max in Sr 10− x RE x (VO 4) 6(OH) 2− x O x on the atomic number of the RE element is shown here with the present data marked with red color.
ISSN:	0022-4596 1095-726X
DOI:	10.1016/j.jssc.2008.06.003