Investigation of structural phase transition behavior by thermal analysis, high temperature X-ray single crystal and vibrational study of Rb2HAsO4⋅Te(OH)6 compound

The differential scanning calorimetry (DSC) analysis of Rb2HAsO4⋅Te(OH)6 (RbAsTe) material shows three phase transitions at 332 K, 464 K and 476 K. In order to identify the first phase transition, we have conducted the X-ray single crystal analysis at high temperature (363 K). X-ray powder diffraction and Raman studies at different temperatures confirmed the presence of the phase transitions in this material as well as the presence of reconstructive phase transition, with such considerable changes of structural parameters. In fact, at T = 363 K, the crystal structure of (RbAsTe) is found to crystallize in the monoclinic system I2/a with the following cell parameters: a = 16.7279(11) Å, b = 7.1339(6) Å, c = 12.4841(10) Å, β = 90.295(6)°, Z = 8, V = 1489.5(2) Å3. At this temperature, the structure is made up of planes of TeO6 groups alternating with those of AsO4 polyhedra. The Rb+ cations are intercalated between these pure planes. crease in temperature affected the structural arrangement in which the coordinated polyhedra are distorted and the “a” lattice cell dimension increases with a slight variation of the other parameters. The planes of octahedra and tetrahedra were parallel to the c direction like those in the structure at room temperature but the planes formed by the cations atoms changed their direction.