Structure and phase transition of Sn-substituted Zr(1-x)SnxW2O8

• Published in: Journal of materials chemistry Vol. 14; no. 20; pp. 2988 - 2994
• Main Authors: DE MEYER, Christy, BOUREE, Francoise, EVANS, John S. O, DE BUYSSER, Klaartje, BRUNEEL, Els, VAN DRIESSCHE, Isabel, HOSTE, Serge
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 21.10.2004
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Physics; Thermal properties of condensed matter; Cubic lattices; Order-disorder transformations; Transition temperature; Zirconium compounds; Inorganic compounds; Phase transformations; Transition element compounds; Tungsten oxides; XRD; Lattice parameters; Tungstates; Phase transitions; Thermal expansion; Dilatometry; Temperature effects; Zirconium oxides; Solid state reaction
• ISSN: 0959-9428; 1364-5501
• DOI: 10.1039/b407851a

A conventional solid state reaction between ZrO2, SnO2 and WO3 was used to prepare the negative thermal expansion material Zr(1-x)SnxW2O8. The strong negative thermal expansion over a broad temperature range, which is well known for the pure zirconium tungstate compound, is also shown in this substituted material. However, the order-disorder phase transition of the cubic materials was shown to shift towards lower temperatures, dependent on the degree of Sn(4+)-substitution, by dilatometry and temperature variable XRD. This is due to the lower bond strength of the Sn-O bond compared to the Zr-O bond. The unit cell parameters of the material are significantly smaller due to the insertion of smaller Sn(4+)-cations on the Zr(4+)-position in the structure. For one composition (x = 0.3), the structure of Zr(1-x)SnxW2O8 was studied by neutron diffraction at two temperatures, 293 K and 473 K, corresponding to respectively the low temperature alpha-, and high temperature beta-polymorph of Zr(1-x)SnxW2O8. The refined structures were found to be similar to that of ZrW2O8 at the same temperatures. Variable temperature XRD of the same sample was used to establish the phase transition temperature, by refining the fractional occupancy of the possible tungstate orientations with temperature. 34 refs.