RESUMEN
PZT based multi-system has shown super piezoelectric properties when the composition was located at morphotropic phase boundary (MPB), which divided the regions into rhombohedral and tetragonal structures equally. In the present paper, the diffuse phase transition and phase coexistence of rhombohedral and tetragonal phases of 0.5PZN-0.5PZT ceramics were investigated by Raman scattering spectroscopy in detail. The results revealed that compared with pure PZT, the width of Raman bands of 0.5PZN-0.5PZT was quite broad, indicating that the system has strong relaxor feature. According to the temperature dependence of dielectric permittivity, the indicator of degree of diffuseness, gamma, was calculated and the values were as high as 1.71. Through the separation by Gauss fitting of the Raman bands, the intensities of different Raman vibration modes, such as the tetragonal E (3TO), A1 (3TO), E (4LO) and A1 (3LO) modes, as well as the rhombohedral R1 and Rh modes, were determined. The results indicated that for 0.5PZN-0.5PZT system, the fraction of rhombohedral phase was equal to the tetragonal phase, which has also been affirmed by XRD results and suggested that the system was close to the MPB. Excellentpiezoelectric properties, such as kp (0.66) and d33 (425 pC/N), were found in 0.5PZN-0.5PZT system, showing a great promise of this system as practical materials for piezoelectric actuators.