Piezoelectric coefficients of PMN-0.29PT single crystals in the temperature range of phase transitions

The temperature dependencies of piezoelectric coefficients d 33 and d 31 for Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 multi-domain single crystals, poled in [001]-direction, were investigated. The two samples had x- and y-axes identical with crystallographic [100] and [010] directions respectively, and the second two samples with [−110] and [110] directions. The laser interferometry method was used for the piezoelectrically induced displacement measurement. Piezoelectric coefficients were similar for all samples at room temperature and were roughly d 31 = −550 pC/N and d 33 = 1,100 pC/N. Very high increase of coefficients to values about d 31 = −2,100 pC/N and d 33 = 3,900 pC/N was observed below temperature of the first phase transition 101 °C. The coefficients exhibited only negligible frequency dependence at room temperature. But coefficient increases of about 10–30% as were observed at temperatures about 98 °C for 1 Hz applied field frequency in comparison to values received at 1 kHz. The second phase transition to cubic phase was observed at the temperature 124 °C. The temperature dependencies of dielectric and piezoelectric coefficients were compared too.