LAUSR

Thermal analysis confirmed the presence of the phase transition at T  = 320 K in the Cs 2 SeO 4 ·H 6 TeO 6 (CsSeTe) material. The structural study carried out at T  = 360 K shows that this compound passes from the monoclinic system with the space group $$P2_{1} /c$$ P 2 1 / c at room temperature, to the trigonal system with the space group $$R\bar{3}m$$ R 3 ¯ m . At room temperature, the anionic groups are well ordered and stable, whereas after the transition at T  = 320 K, the selenate groups change their orientation and the tellurate polyhedra change their positions. The high-temperature vibrational studies, carried out in a temperature range of 289–353 K, confirm the presence and nature of the transition detected by thermal analysis. The conductivity evolution versus temperature shows the presence of an ionic–protonic conduction phase transition at T  = 490 K.