Poling effect on the piezoelectric properties of lead zirconate titanate thin films

The effect of poling on the piezoelectric properties of sol-gel derived PbZr_0.45Ti_0.55O₃ (PZT) thin films is investigated by laser interferometry. Poling conditions are varied in order to optimize the longitudinal piezoelectric coefficient (d₃₃) of the films. Short-term aging of d₃₃ is also studied to predict the piezoelectric behavior as a function of time. The aging rate and d₃₃ values are found to saturate when sufficiently high electric field (~200 kV/cm) is applied at room temperature. Further improvement of the piezoelectric properties is achieved with the increase of poling temperature (up to 150°C). The poling effect at high temperature is found to correlate with the built-up of an internal bias field, which is responsible for the stabilization of the domain structure. Photoinduced poling using illumination with ultraviolet (UV) light is shown to be an alternative way to improve the piezoelectric properties of films poled at room temperature. The mechanism of the poling effect in PZT thin films is discussed