Order disorder phase transitions in the cesium sulfate arsenate tellurate compound

• CsSAsTe presents a reversible phase transition at 213/211 K on heating–cooling runs.
• CsSAsTe crystallizes, at T = 120 K, in the monoclinic system P21/c.
• CsSAsTe crystallizes, at T = 275 K, in the trigonal system R3¯c.
• (S/As)O4 tetrahedra are the main disordered units in the structure.

Cesium sulfate arsenate tellurate (CsSAsTe) presents one reversible phase transition of the first-order type at 213/211 K on heating–cooling runs. Indeed, it crystallizes at T = 120 K in the monoclinic system P21/c and at T = 275 K, in the trigonal system R3¯c  . These crystal structures are built from isolated (HAsO42−, SO42−) tetrahedra and (TeO66−) octahedra, they form tunnels where Cs+ cations and some hydrogen atoms are placed. The cohesion of these structures is assured on the one hand by the interaction between Cs+ and the oxygen atoms and on the other hand, by the presence of hydrogen bonds.

Projection of the structure of the new CsSAsTe material at 120 K.Figure optionsDownload as PowerPoint slide