High-temperature synchrotron X-ray powder diffraction study of Cs2XSi5O12 (X = Cd, Cu, Zn) leucites

Synchrotron X-ray powder diffraction data have been collected on three synthetic leucite analogues with the general formula Cs2XSi5O12 (X = Cd, Cu, Zn) between 295 and 1173 K. All three samples have the orthorhombic Pbca leucite structure at room temperature with ordered framework T-site cations. The sample with X = Cd retains the Pbca structure over the whole of the investigated temperature range. The sample with X = Cu also retains the Pbca structure, but there is a transition to a less distorted structure with a larger unit-cell volume at ~333 K. The sample with X = Zn shows evidence for a transition to a previously unknown Pa3¯ cubic structure, with some T-site cation disorder, at 566 K, on heating. This transition is reversible on cooling to 633 K.