Automatic performance testing of piezoelectric ceramics for power transducers

The suitability of piezoceramics for transducers of high ultrasonic power is limited by dielectric and mechanical losses, which are intensified in the case of high electric field strengths and large mechanical stresses within the ceramics. A fully automatic system for measuring the mechanical losses and elastic coefficients of piezoceramics as a function of the elastic stresses is described.Measurements on lead zirconate titanate ceramics modified with Mn and Nb show the mechanical losses in the ceramic as well as its elastic coefficient to increase sharply as of a certain amplitude of mechanical stress. This mechanical threshold stress depends on the Mn mole fraction and degree of domain-wall stabilization in the ceramic.