Very pure lead zirconate titanate ceramics were prepared for an accurate determination of the characteristic values of piezoelectric properties. The ceramics were sufficiently matured by using pulverized calcined powders and by sintering with a gradual rise in temperature. Electromechanical activity of the ceramics became maximum when the ceramics were subected to poling at 100°C with a field intensity of 40 kV/cm for 10 min. Deterioration gave rise to the breakdown of ceramics along grain boundaries when the field intensity and the time of poling increased. Breakdown predominated in the ceramics belonging to tetragonal symmetry.
Breakdown seems to be caused by a decrease of intergranular binding strength, and this assumption was confirmed by measurement of the bending strength and observation of the fracture.