Dielectric and piezoelectric properties of 0.91pb(zn_1/3nb_2/3)o₃-0.09pbtio₃ single crystals

The dielectric, piezoelectric and elastic properties of 0.91(PbZn_1/3Nb_2/3)O₃舑0.09PbTiO₃ single crystals have been investigated as functions of temperature and applied electric field. Two multiple phase transitions at 68ŶC and 178ŶC, the crystal changing from the rhombohedral ferroelectric phase to tetragonal ferroelectric and then to cubic paraelectric, have been observed. Both the transitions are of first-order, but both are slightly diffused. Significant increases in the dielectric, piezoelectric and elastic constants are observed at the lower transition point. In particular, the sample poled along the pseudo-cubic [001] axis reveals anomalously large piezoelectric and electro-mechanical coupling constants at room temperature in the rhombohedral phase (d_[001]//=1500ȕ10^-12 C/N, k_[001]//=0.92).