Features of manifestation of surface electrochemical processes in ferroelectric crystals with low−temperature phase transitions

Abstract. The process of short circuit current behaviour in crystals with low−temperature phase transitions Rochelle salt NaKC₄H₄O₆ • 4H₂O and triglycine sulfate (CH₂ • NH₂ • COOH)₃ • H₂SO₄ was studied. The investigations were carried out on samples of polar cuts without preliminary polarization with symmetrical indium conductive coatings. Short−circuit currents which persist for a rather long time were observed on all samples already at room temperature. The phenomenon of current decay with time was observed. The temperature dependences of short−circuit currents were obtained in the temperature range 17—45 °С for Rochelle salt, in the temperature range 17—110 °С for triglycine sulfate. Short−circuit currents are observed in these crystals both in the ferroelectric phase and in the paraphase. It is shown that in a ferroelectric phase, the total short−circuit current is determined by the competing processes — pyro−currents and currents of electrochemical decomposition. In the paraphase, the short−circuit currents are the currents of electrochemical self−decomposition. Based on the experimental results obtained in this work, it was shown that the flow of short−circuit currents through the samples of polar sections of crystals of Rochelle salt and triglycine sulfate is due to the presence of its own EMF resulting from electrochemical self−decomposition of the opposite surfaces of the polar sections of the samples in contact with conductive coatings due to anisotropy of these surfaces. A model of electrochemical self−decomposition in such crystals is proposed.

polar classes, ferroelectrics, triglycine sulfate, Rochelle salt, low−temperature ferroelectric phase transition, pyroelectric effect, short−circuit currents

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