PHASE-BEHAVIOR OF RBH2PO4 AND CSH2PO4 IN THE FAST-ION REGIME

Results of thermal analysis in CsH2PO4 (CDP) and RbH2PO4 (RDP), using combined differential scanning calorimetry (DSC) and high-resolution ac calorimetry, are presented. For single crystal samples, a sequence of phase transitions in both salts above room temperature is found that is very dependent of their thermal treatments. For CDP, the ac data show a broad heat capacity anomaly near T1 = 420 K for freshly prepared samples at room temperature or non-annealed samples above T2 = 500 K, and an endothermic peak at T2 on heating runs and at 470 K on cooling runs. For RDP, much more variations were observed in the region where two transitions were previously reported for different prepared samples that occurred near 352 K and 380 K, respectively.