Features of the Manifestation of Surface Electrochemical Processes in Ferroelectric Crystals with Low-Temperature Phase Transitions

Abstract

The short-circuit current flow in crystals with the low-temperature phase transitions including Rochelle salt NaKC4H4O6 · 4H2O and triglycine sulfate (CH2 · NH2 · COOH)3 · H2SO4 is investigated. The experiments are conducted on polar cut samples without preliminary polarization with the symmetric indium conducting coatings. The short-circuit currents remaining for a fairly a long time and the current decay with time are observed at room temperature on all the samples. The temperature dependences of the short-circuit currents in the temperature ranges of 16 to 45°С for Rochelle salt and 16–110°С for triglycine sulfate are obtained. The short-circuit currents are observed in these crystals both in the ferroelectric and paraphase. It is shown that, upon heating in the ferroelectric phase, the total short-circuit current is determined by competing processes: the pyroelectric currents and electrochemical decomposition currents. In the paraphase, the short-circuit currents are the electrochemical self-decomposition currents. Based on the experimental results obtained, it is demonstrated that the short-circuit current flow through the polar cut samples of Rochelle salt and triglycine sulfate crystals is induced by the intrinsic emf caused by the electrochemical self-decomposition of the opposite surfaces of the sample polar cuts when in contact with the conducting coatings due to the anisotropy of these surfaces. A model of the electrochemical self-decomposition in such crystals is proposed.