Impedance Spectra near the Phase Transition Temperature of Potassium Lithium Niobate Crystals

Abstract

The impedance spectroscopy of potassium lithium niobate (KLN) crystals was investigated over the frequency range of 100 Hz to 1 MHz in the temperature region of room temperature to 600°C. Above and below the phase transition temperature, the AC complex impedance is explained by the Cole-Cole semi-circle, with a temperature-dependent factor indicating the degree of distribution of the relaxation time. However, near the phase transition temperature, a skewed semi-circle was found. The frequency dispersion of the AC complex impedance near the phase transition temperature is different from that above and below the phase transition temperature. The two distinct slopes and the differences in the frequency variation of the imaginary part of impedance suggest that two dispersion mechanisms are involved. In the vicinity of the phase transition temperature at a low frequency, the AC complex impedance is influenced by a mobile charge carrier.