Phase transitions and vibrational study of Rb₂SeO₄·Te(OH)₆and Rb_1.12(NH₄)_0.88SO₄·Te(OH)₆

Structural, calorimetric and conductivity study of the new mixed solution Rb2(SO4)0.5(SeO4)0.5Te(OH)6

“…The (RbSeTe) material exhibits three endothermic phase transitions at 430, 470 and 493 K. These transitions are characterized by dielectric measurements and spectroscopic study at different temperatures. This fact shows that the first phase transition at 430 K is of structural type which favors the polar phase at high temperature, the second one at 470 K is related to a ferro-paraelectric phase transition, whereas the third one is of protonic conduction type [9]. In order to examine the effect of partial anionic substitution over structural and electrical properties, we have extended these investigations to Rb 2 (SO 4 ) x (SeO 4 ) 1−x Te(OH) 6 .…”

Structural, conductivity and dielectric studies in (NH4)2SeO4·Te(OH)6

“…3, which shows the diagram obtained by heating a freshly prepared sample from 300 to 700 K. The thermogram reveals three endothermal peaks at 415, 433 and 443 K. The calculated transition enthalpy for the first transition at T = 415 K is H 1 = 122.18 J g −1 , for the second transition at T = 433 K is H 2 = 12.18 J g −1 and for the third one at T = 443 K is H 3 = 10.5 J g −1 . By comparing the thermograms of Rb 2 SeO 4 ·Te(OH) 6 and K 2 SeO 4 ·Te(OH) 6 , we note that the anomaly at 415 K can be attributed to the structural phase transition which can favor a non-centrosymmetric phase at high temperature [7,20]. The anomaly at about 433 K is probably due to the ferro- paraelectric phase transition, whereas the peak at about 443 K can be related to the protonic-ionic conduction type.…”

“…M 2 SeO 4 ·Te(OH) 6 where M = K, Cs and Rb have also been analyzed. The potassium selenate, K 2 SeO 4 ·Te(OH) 6 and ammonium sulfate tellurate (NH 4 ) 2 SO 4 ·Te(OH) 6 are isostructural and crystallize in the monoclinic space group Cc, whereas Cs 2 SeO 4 ·Te(OH) 6 and Rb 2 SeO 4 ·Te(OH) 6 are monoclinic with P2 1 /c space group [6,7,20].…”

“…These properties are due to the presence of a hydrogen bond, which link all the polyhedra and the variation of the size of the monovalent cation. In fact, K 2 SeO 4 ·Te(OH) 6 and Rb 2 SeO 4 ·Te(OH) 6 have a ferro-paraelectric phase transition, respectively, at 433 and 470 K and a super-protonic conduction one at 480 and 490 K [7,20].…”

Synthesis, Characterization and X-ray Crystal Structures of the New Mixed Compound Rb1.89Na0.11(SO4)0.89(SeO4)0.11Te(OH)6

“…By comparison with other compounds, the first transition of our material at 412 K can be attributed to the structural phase transition, which can favor a non centrosymmetric phase at high temperature [10]. The anomaly at 467 K can be attributed to the ferro-paraelectric phase transition.…”