Proton dynamics and low-temperature (1.5-130 K) pyroelectric coefficient anomalies of KDP-single crystals

In order to explain the observed anomalous behavior of the KH2PO4 pyroelectric coefficient at low temperatures (T < 20 K), a two component model is proposed. In the field of the main component of matrix spontaneous polarization Psm(T), whose temperature change is determined by anharmonic ideal crystal lattice vibrations, an additional component Psm(T) is formed, due to the low temperature dynamics of proper elements of KH2PO4 structure (protons). The proposed mechanism of formation of the Psad(T) and γ/sigmaad(T) is a phase transition “polar phase—polar phase” in the proton subsystem with Tc = 21-23 K. It has been established that the γ/sigmaad(T) shape depends on the previous history of growth of the samples, their defects and prior heat annealing.

Keywords:

• Pyroelectric coefficient
• low temperature
• KDP