Novel high power piezoelectrics for transformers and actuators

This letter reports a Pb(Zr_0.5Ti_0.5)O₃ (PZT) based composition, which provides high dielectric, piezoelectric and electromechanical properties. The composition corresponding to 0.2 PZN - 0.8 PZT + 0.5 wt% MnO₂ provides the radial mode coupling factor (k _p) of 0.58, longitudinal mode piezoelectric constant (d₃₃) of 277 pC/N, dielectric constant (ε₃₃/ε_o) of 946 and mechanical quality factor (Q_m) of 1402. X-ray diffraction, dielectric and polarization-electric field measurements were done to investigate the origin for this high performance. It was found that high soft properties are obtained due to the shifting of PZT composition towards morphotropic phase boundary (MPB) and high hard properties are obtained due to the generation of dipolar defects which pin the polarization. The properties of the composition corresponding to 0.9 PZT - 0.1PMnN (Zr/Ti = 0.51/0.49) modified with 6 mol% Sr were found to be: k_p = 0.53, Q_m = 800, d₃₃ = 274, e₃₃/ε_o = 1290 and tanδ = 1.1%, with a TCF of -8 ppm/°C (-20 to 80°C). High piezoelectric properties with low TCF shows the suitability of this composition for ultrasonic devices used under fluctuating thermal environment.