Crystal structure and thermal expansion of the low- and high-temperature forms of BaM{sup IV}(PO{sub 4}){sub 2} compounds (M=Ti, Zr, Hf and Sn)

Journal Article · Fri May 15 00:00:00 EDT 2009 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2009.02.012· OSTI ID:21370386

Bregiroux, D ^[1]; Popa, K ^[2]; Jardin, R; Raison, P E ^[3]; Wallez, G; Quarton, M ^[1]; Brunelli, M; Ferrero, C ^[4]; Caciuffo, R ^[3]

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1. UPMC Univ. Paris 06, CNRS-UMR 7574, ENSCP-ParisTech, Laboratoire de Chimie de la Matiere Condensee de Paris, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France)
2. 'Al.I. Cuza' University, Department of Chemistry, 11-Carol I Blvd., 700506 Iasi (Romania)
3. European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, 76125 Karlsruhe (Germany)
4. ESRF, 6 rue Jules Horowitz, BP 220-38043 Grenoble Cedex (France)

The crystal structure of beta-BaZr(PO{sub 4}){sub 2}, archetype of the high-temperature forms of BaM(PO{sub 4}){sub 2} phosphates (with M=Ti, Zr, Hf and Sn), has been solved ab initio by Rietveld analysis from synchrotron X-ray powder diffraction data. The phase transition appears as a topotactic modification of the monoclinic (S.G. C2/m) lamellar alpha-structure into a trigonal one (S.G. P3-barm1) through a simple mechanism involving the unfolding of the [Zr(PO{sub 4}){sub 2}]{sub n}{sup 2-} layers. The thermal expansion is very anisotropic (e.g., -4.1<alpha{sub i}<34.0x10{sup -6} K{sup -1} in the case of alpha-BaZr(PO{sub 4}){sub 2}) and quite different in the two forms, as a consequence of symmetry. It stems from a complex combination of several mechanisms, involving bridging oxygen rocking in M-O-P linkages, and 'bond thermal expansion'. - Graphical abstract: The layered high-temperature form of BaM(PO{sub 4}){sub 2}, only expands along the c-axis.

• OSTI ID: 21370386
• Journal Information: Journal of Solid State Chemistry, Vol. 182, Issue 5; Other Information: DOI: 10.1016/j.jssc.2009.02.012; PII: S0022-4596(09)00071-1; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM PHOSPHATES
HAFNIUM COMPOUNDS
LAYERS
MONOCLINIC LATTICES
PHASE TRANSFORMATIONS
THERMAL EXPANSION
TIN COMPOUNDS
TITANIUM COMPOUNDS
X-RAY DIFFRACTION
ZIRCONIUM COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
COHERENT SCATTERING
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DIFFRACTION
EXPANSION
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
REFRACTORY METAL COMPOUNDS
SCATTERING
TRANSITION ELEMENT COMPOUNDS