DURABILITY OF PIEZOELECTRIC CERAMICS FOR AN ACTUATOR

Change of piezoelectric properties with the number of loading cycles was measured under various driving conditions, i.e., temperature, preset pressure and driving voltage. Although epsilon33T/epsilon0 changed very little, K(p) decreased markedly. K(p) decrease is affected by driving condition factors, i.e., minus voltage, preset pressure and temperature, in that order. By optimal arrangement of these factors, K(p) decrease could be reduced considerably. K(p) decrease is mainly due to 90-degrees switching of the domain. Improvement of mechanical strength for the piezoelectric material is effective both for the suppression of microcrack occurrence and for prevention of K(p) decrease. We found that microcrack occurrence caused domain switching. We suggest a deterioration mechanism for piezoelectric ceramics.