Mechanical and electric fatigue of PZT(53/47) films on metallic substrates

We have investigated the fatigue of electromechanical and dielectric properties of sol-gel derived PZT(53/47) thin films deposited on metallic substrates by means of electric and mechanical cycling. For the mechanical cycling a two point bending. method was used to apply transversal stress to the samples. During mechanical cycling the piezoelectric coefficient d(31) remained constant up to about 10(5) cycles, for a higher number of cycles a strong decrease was observed. During electric cycling no significant changes in the ferroelectric and electromechanical hysteresis loops could be found up to about 3x10(5) cycles. Above this number the coercive field increases, the maximum strain and the remanent polarization decrease. Obviously each electric cycling of the investigated films is accompanied by a mechanical cycling. It is assumed, that microcracks induced by mechanical stress are the main reason for the deterioration of the physical properties films during electric and mechanical cycling both.