Pressure-induced phase transformation in ZrW2O8 -: Compressibility and thermal expansion of the orthorhombic phase

In situ neutron powder diffraction has been used to show that the application of hydrostatic pressure at room temperature produces a transformation of ZrW2O8 from the cubic to an orthorhombic phase beginning at 2.1 kbar and completed by 3.1 kbar, with a 5% reduction in volume. After release of pressure, the orthorhombic phase is retained at room temperature. Its thermal expansion is negative below room temperature, but is positive above room temperature with a transformation back to the cubic phase at about 390 K. The WO4 groups are found to play the dominant role in both phase transformations. The volume compressibilities of the cubic and orthorhombic phases are 1.38 x 10(-3) and 1.53 x 10(-3) kbar(-1). respectively. (C) 1998 Published by Elsevier Science B.V. All rights reserved.