Dielectric and Thermal Studies on New Phase Transitions of CsHSO₄

Interrelationship between superprotonic conductivity and strain in CsHXO4

“…The CsHXO 4 compounds belong to the monoclinic system with the point group of 2/m below T c [8][9][10]. On the other hand, above T c , CsHXO 4 belongs to the tetragonal system with the point group 4/m [3,11]. Accompanied by the change of crystal symmetry, the equivalent position of proton in the high-temperature superprotonic phase in these compounds becomes 4 times larger than that in the low-temperature phase * Corresponding author.…”

Superionic phase transitions in hydrogen bonded crystals

“…I n the disordered superionic phase a t T 2 T , in CHS and CHSe n ( T ) = no, the total density of protons in crystals [6], while in the ordered phase a t T < T , the density of defects in the lattice can be estimated as three-proton configurations: n ( T ) = no exp ( T,. -!Po = 5.5 x 10-3T, = 2.5 K and the entropy change a t the phase transition given by (28) is 68 = 0.58 R. The latter is considerably smaller than the experimental one in CHS [17] 6 8 N 1.32 R as well as in CHSe [18] 6 s N 1.93 R. This discrepancy is apparently due t o the fact that in the present model only the disordering of protons is taken into account while all other degrees of freedom are disregarded. In experiments (see [3, 61) a considerable change in the lattice dynamics at the phase transition in CHS, CHSe, and RbHSeO, is observed and in a more general model it should be taken into account.…”

Notizen: New Phase Transitions in CsHSeO4, CsH2PO4, RbHSO4, RbHSeO4, and RbH2PO4

“…However, it cannot be excluded that part of the measured enthalpy change might be due to some loss of water from the salt. Anyway, we face here a different class of orderdisorder transitions than those occurring at some what higher temperatures in C sH S 04 [10], CsHSe04 [11] and^RbHSe04 [7,8],…”