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

Abstract

For use in ultrasonic actuators, we investigated the structural and piezoelectric properties of <TEX>$(1\;-\;x)Pb(Zr_{0.515}Ti_{0.485})O_3$</TEX> - <TEX>$xPb(Sb_{1/2}Nb_{1/2})O_3$</TEX> + 0.5 wt% <TEX>$MnO_2$</TEX> [(1 - x)PZT - xPSN + <TEX>$MnO_2$</TEX>] ceramics with a variation of x (x = 0.02, 0.04, 0.06, 0.08). All the ceramics, which were sintered at <TEX>$1250^{\circ}C$</TEX> 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 <TEX>$1.3{\mu}m$</TEX> 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+<TEX>$MnO_2$</TEX> ceramics, which corresponds with a morphotropic phase boundary (MPB) composition in the (1 - x)PZT - xPSN + <TEX>$MnO_2$</TEX> system, exhibited good piezoelectric properties: a piezoelectric constant (<TEX>$d_{33}$</TEX>) of 325 pC/N, an electromechanical coupling factor (<TEX>$k_p$</TEX>) of 70.8%, and a mechanical quality factor (<TEX>$Q_m$</TEX>) of 1779. The specimens with a relatively high curie temperature (<TEX>$T_c$</TEX>) of <TEX>$305^{\circ}C$</TEX> also showed a significantly high dielectric constant (<TEX>${\varepsilon}_r$</TEX>) value of 1109. Therefore, the 0.96PZT - 0.04PSN + <TEX>$MnO_2$</TEX> ceramics are suitable for use in ultrasonic vibrators.