Abstract: The piezoelectric constants d₃₃ and d₃₁ under weak and stronger field were measured from strain S vs electric field E curves
for the converse piezoelectric effect. It was shown that on the curves there is a critical field E_b from which strains and d₃₃, d₃₁ were obviously increased, and the result was discussed in the view of reorientation of 90° domain
intrinsically existed in piezoelectric ceramics. This method of measuring d₃₃, d₃₁ is simple and convenient, as well as more
practical, especially for piezoelectric ceramic actuator, as compared with that usually obtained them from positive piezoelectric effect.

Key words: piezoelectric constant, converse piezoelectric effect, piezoelectric ceramics actuator