Tetragonal‐to‐Cubic Structural Phase Transition in Pollucite by Low‐Temperature X‐ray Powder Diffraction

The tetragonal‐to‐cubic structural phase transition in pollucite (CsAlSi ₂ O ₆ ) 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 CsAlSi ₂ O ₆ had a tetragonal phase with a space group of I 4 ₁ /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.