High temperature phase transitions and proton conductivity in some kdp-family crystals

The high temperature phase transitions and conductitivity have been studied in some single crystals of the alkaly dihydrogen phosphates and dihydrogen arsenates. The quite different nature of the high temperature phase transitions in KDP and RDP in contrast with those in CDP and CDA is established. It is shown that the high temperature cubic phases in CDP and CDA are superionic ones. The experimental results are analyzed in terms of proton transport model, taking into consideration the migration of protons between normal and interstitial proton sites.