Tetragonal-to-Cubic Structural Phase Transition in Pollucite by Low-Temperature X-Ray Powder Diffraction.

The tetragonal-to-cubic structural phase transition in pollucite (CsAlSi2O6) was investigated using low-temperature X-ray powder diffraction in the temperature range of 93 to 298 K, and the lattice constants were refined with Rietveld analysis. It was found that CsAlSi2O6 had a tetragonal phase with a space group of I41/acd in the temperature range of 93 to 248 K, a = 1.36337(4) nm, c = 1.36988(6) nm at 248 K, and underwent a phase transition from tetragonal to cubic with a space group of Ia-3 in the temperature range of 248 to 273 K, a = 1.36645(3) nm at 273 K.