Low-temperature sintering of MnO2-doped PZT–PZN Piezoelectric ceramics

The effect of MnO2 addition on the microstructural evolution and piezoelectric properties of low temperature sinterable PZT–PZN ceramics was investigated. When a small amount of MnO2 (≤0.5 wt% ) was added, the Mn ions were homogeneously dissolved in the PZT– PZN ceramics, leading to full densification at a temperature as low as 930 °C. However, the further addition of MnO2 hindered the densification, causing the specimen to have a high porosity and small grain size. In addition, as the MnO2 content increased, the crystal structure of the PZT–PZN changed gradually from a tetragonal to a rhombohedral phase, due to the substitution of Mn for the B-sites in the perovskite structure. The addition of MnO2 up to a maximum of 0.5% improved the mechanical quality factor (Qm) of the PZT–PZN ceramics markedly, while keeping the kp and d33 values reasonably high. The 80% PZT–20% PZN doped with 0.4 wt% MnO2 exhibited excellent piezoelectric properties; Qm=1,000, kp=0.62, and d33= 330 pC/N.