Growth and characterization of piezo-/ferroelectric Pb(Mg _1/3Nb_2/3)O₃PbTiO₃Bi(Zn _1/2Ti_1/2)O₃ ternary single crystals

In order to develop new piezo-/ferroelectric materials, single crystals of the Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃- Bi(Zn_1/2Ti_1/2)O₃ [PMN-PT-BZT] ternary complex perovskite system has been grown by a high temperature solution method using the mixture of PbO and H₃BO₃ as flux (in a molar ratio of 4:2) with an optimum flux:charge molar ratio of 6:1. It is found that the addition of BZT into the relaxor ferroelectric PMN-PT system reduces the number of spontaneous nucleations, resulting in large single crystals (5 mm×5 mm×14 mm) of good quality. The grown crystals exhibit a pseudo-cubic morphology and show evidence of two-dimensional growth mechanism. Examination by polarized light microscopy (PLM) reveals the formation of striation, which can be reduced by changing the growth conditions. The domain structure and phase transition of the PMN-PT-BZT crystals are investigated by PLM. The temperature and frequency dependences of the dielectric permittivity of the grown crystals show typical relaxor ferroelectric behavior, with the frequency dependence of the temperature of maximum permittivity (T_max) following the VogelFulcher law. The ferroelectric property is displayed in the crystals with a remnant polarization, P_r=21 μC/cm² and a coercive field, E_C=3.5 kV/cm. The piezoelectric coefficient, d₃₃, is found to be 825 pC/N, a value much higher than that of the ternary ceramics.