Characterisation of piezoceramic under uniaxial stress

An experimental set up has been developed for monitoring the static stress influence, up to 120 Mpa, on the dielectric /spl epsiv//sub 33/ piezoelectric and d/sub 33/ mechanical s/sub 33/ coefficients. For these coefficients, the same trends are always observed: an increase for moderate static stress followed by a decrease for higher stress. In a general manner, the soft material presents stronger variations, with a large hysteresis, than hard materials. By introducing dopants to block off the oxygen vacancies, the coefficients variations and the hysteresis loop are strongly reduced. A theoretical analysis leads to the different relationships between the variations of the considered coefficients versus the applied stress.