Peculiarities in the electrical conductivity and pyroelectric behavior of thin samples of PLZT 8/65/35

Abstract

Abstract We have studied the electric currents in 20 and 10 m. thick samples of PLZT 8/65/35, j under constant electric fields of 0 to 100 kV/cm, with heating the samples from 20 to up to 16O°C, and subsequent cooling to room temperature. The samples had a vacuum deposited InSb electrode, usually connected to the positive output of the power supply, and on the opposike large surface - a gold electrode, connected to a picoammeter. The recorded current vs. temperature curves show an initial decrease, cross the 0 line and indicate a negative current, flowing in the direction opposite to the applied electric field. The negative current; has several minima at field-dependent temperatures, which disappear under higher fields, except for a main minimum, which remains at all. fields above 35 kV/cm. The temperature Tm of the occurrence of the main minimum is then field independent and varies between 45 and 60°C in different samples. It therefore should be connected with the known 55°C phase transition.2 With a lower heating rate at higher temperatures, the current becomes positive, reaching values similar to the initial ones (10−10 - 10− 12A). During the slow cooling to room temperature, the current remains positive, decreasing to a final three to Tour orders of magnitude lower value. The electrical conductivity and the pyroelectric coefficient are derived as functions of temperature and field with the known heating rates.