Domain contribution to direct and converse piezoelectric effects of PZT ceramics

The domain contributions in the piezoelectric converse effect and the direct effect were compared for soft- and hard-PZTs (lead ziroconate and lead titanate solid solitions) by measuring piezoelectric constant d(33) as a function of frequency. The d(33) of the converse effect was determined from the electric-field induced strain. In the measurement of the direct effect, a sinusoidal stress was applied to the sample using a piezoelectric actuator and the polarization generated by the direct effect was detected as a displacement current. The degree of the domain contribution was estimated from the difference in the piezoelectric d(33) constants determined from the resonance method and that from the converse or the direct effect. The domain contribution was larger in the soft-PZT than in the hard-PZT. The d(33) determined from the two effects was consistent in the soft-PZT but the d(33) of the hard-PZT determined from the direct effect was markedly larger than that from the converse effect or the resonance method. These results indicated that a fairly large degree of the domain contribution existed in the direct effect of the hard-PZT, and that the mechanism of the domain wall clamping did not work effectively in the direct effect.