Current leakage and transients in ferroelectric ceramics under high humidity conditions

Lead zirconate titanate (PZT) is widely used in electromechanical devices such as ultrasonic transducers, sensors, ultrasonic motors, actuators and resonators. In harsh operating environments such as high humidity and high temperature the electrical resistance of the ceramic can decrease resulting in leakage currents. These can have a significant impact on device performance, particularly for low power applications. In this paper, the increase in leakage current is investigated and characterised under high humidity conditions. It is observed that the leakage current does not evolve smoothly over time, but is characterised by current transients. Detailed measurements of these current transients are reported, and their relationship to the conduction processes in the ceramic is investigated. A mechanism of conductive channel formation is proposed to account for the leakage current increase and current transients.