Piezoelectric properties and phase transitions of 〈001〉-oriented Pb(Zn_1/3Nb_2/3)O₃-PbTiO₃ single crystals

Electric-field-induced phase transitions and piezoelectric properties of 〈001〉-oriented Pb(Zn_1/3Nb_2/3)O ₃-xPbTiO₃ single crystals for x=4.5% and 8% (PZN-4.5%PT and PZN-8%PT) have been investigated as a function of temperature. It was found that the piezoelectric properties and phase transitions for both crystals are strongly dependent on temperature. The measurements of polarization and strain as a function of unipolar electric field show that the field for the rhombohedral-tetragonal phase transition decreases linearly with temperature in the range between 25 and 105°C. Thus, raising the temperature can stabilize the tetragonal phase in 〈001〉-oriented PZN-PT crystals. Longitudinal piezoelectric constant d₃₃ in the rhombohedral phase increases with temperature for both crystals; in PZN-4.5%PT the slope itself increases significantly at temperatures over 60°C. In the field-induced tetragonal phase, there is little change in d₃₃ for PZN-8%PT within the temperature range investigated, while in PZN-4.5%PT a slight increase of d ₃₃ with temperature was observed at temperatures above 80°C.