Pyroelectric Response in LiNbO3 and LiTaO3 to Temperature Changes

Abstract

Measurements of the polarization charge accumulated at the -z and the +z bases of the pyroelectric crystals of LiNbO3 and LiTaO3 during changes in temperature are described. An electrometer in the charge mode with its probe attached to the base under study was used. A reference for the electrometer was established by grounding the electrometer probe at a specific crystal temperature, i.e., zeroing the electrometer. When the ground is broken an induced charge, held captive by the polarization charge at the base of the crystal, remains in the probe circuit. Then as the temperature of the crystal is changed the electrometer reads the change in the polarization charge with respect to the polarization charge at the zeroing temperature. Data was obtained for each type of crystal and at the -z and +z bases for three different grounding conditions. Each experiment consisted of data accumulation for five thermal cycles. The electrometer readings at a given temperature appeared to be different for the three grounding conditions but the difference in the charge readings for a given difference of temperature was independent of the grounding situation. Measurements of the polarization charge were taken while the temperature of the crystal was held constant for about fourteen hours. The polarization charge remained constant at the -z and +z base as long as the temperature remained constant. These results, the independence of the charge difference for a given temperature difference with respect to the zeroing conditions and the constancy of the charge reading with respect to the constancy of the crystal temperature, lead to the inference that the polarization charge is a reproducible function of the crystal temperature and is a physical property of the crystal.