Analysis of phase transition and expansion behaviour of Al2(WO4)3 by temperature‐regulated X‐ray diffraction

Abstract

AbstractX‐ray diffraction measurements of Al2(WO4)3 were carried out under various temperatures from 123 K to 373 K. Diffraction patterns above 273 K and below 253 K could be successfully explained as orthorhombic Pbcn (No. 60) and monoclinic P21/n (No. 14) with superstructure, respectively, which were in agreement with the results of convergent‐beam electron diffraction. Thermal expansion of low‐temperature monoclinic phase and slight shrinkage of high‐temperature orthorhombic phase were observed from the temperature dependence of lattice constants and molar volume, showing agreement with the result of dilatometry. It is revealed that abrupt expansion of Al2(WO4)3 at the structural phase transition is attributed to an abrupt increase of the c‐axis, which is parallel to the 21 screw axis and perpendicular to the n‐glide plane. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)