INSTABILITIES IN THE PIEZOELECTRIC PROPERTIES OF FERROELECTRIC CERAMICS

The large piezoelectric effect of ferroelectric ceramics is utilized i n many devices for sensing and actuating purposes. In this paper, the longitudinal direct piezoelectric effect in ceramics based on lead zir conate titanate, lead titanate, barium titanate and bismuth titanate i s investigated as a function of the amplitude and frequency of the ext ernal pressure, the crystal structure and microstructure of the cerami cs. The domain-wall contribution to the piezoelectric response appears to be a dominant extrinsic origin of instabilities in the observed pi ezoelectric effect but, for a given composition, it can be affected by dopants and microstructure. Other sources of instabilities in the pie zoelectric response, such as chemical inhomogeneities and defects, are also discussed. It is shown that, with proper modifications, it is po ssible to freeze out completely the extrinsic part of the piezoelectri c response in some of the examined compositions and to obtain a stable behaviour, independent of the frequency and magnitude of the external driving held.