Structural and Piezoelectric Properties of MnO2-Doped PZT-PSN Ceramics for Ultrasonic Vibrator

For use in ultrasonic actuators, we investigated the structural and piezoelectric properties of (1 - x)Pb(Zr-0.515 Ti-0.485)O-3 - xPb(Sb1/2Nb1/2)O-3 + 0.5 wt% MnO2 [(1-x)PZT - xPSN + MnO2] ceramics with a variation of x (x = 0.02, 0.04, 0.06, 0.08). All the ceramics, which were sintered at 1250 degrees C for 2 h, showed a typical perovskite structure, implying that they were well synthesized. A homogeneous micro structure was also developed for the specimens, and their average grain size was slightly decreased to 1.3 mu m by increasing x to 0.8. Moreover, a second phase with a pyrochlore structure appeared when x was above 0.06, which resulted in the deterioration of their piezoelectric properties. However, the 0.96PZT-0.04PSN + MnO2 ceramics, which corresponds with a morphotropic phase boundary (MPB) composition in the (1 - x)PZT - xPSN + MnO2 system, exhibited good piezoelectric properties: a piezoelectric constant (d(33)) of 325 pC/N, an electromechanical coupling factor (k(p)) of 70.8%, and a mechanical quality factor (Q(m)) of 1779. The specimens with a relatively high curie temperature (T-c) of 305 degrees C also showed a significantly high dielectric constant (epsilon(r)) value of 1109. Therefore, the 0.96PZT - 0.04PSN + MnO2 ceramics are suitable for use in ultrasonic vibrators.