This study investigated the microstructure and piezoelectric properties of lead-free 0.74(Bi_1/2Na_1/2)TiO3-0.26SrTiO₃ (BNST26) piezoelectric ceramics sintered using a microwave furnace. For comparison, specimens were also prepared using a conventional furnace sintering (CFS). Average grain sizes of 2.4 μm and 3.2 μm were obtained in the sample sintered at 1,100℃ for 5 min using microwave sintering (MWS) and at 1,175℃ for 2 h using CFS, respectively. To quantify the changes in the microstructures and electrical properties according to the sintering conditions, the polarization hysteresis, bipolar and unipolar strain curves, and temperature dependence of permittivity were evaluated. As a result, it was determined that the Pmax (maximum polarization), Pr (remanent polarization) and Smax (maximum strain) values tend to increase with the average grain size. Based on these results, it is concluded that the MWS method can produce lead-free ceramics with superior performance in a relatively short time compared to the conventional CFS method.

A comparative study has been attempted for microwave and conventional sintering of lead-freeBi0.5Na0.5TiO3(BNT)-based multilayer ceramic actuators(MLAs). It was found that microwave sintering(MWS) could be successfully applied to the co-firing of piezoceramic/AgPd MLAs with a 10 timesshorter firing cycle as well as 100℃ lower firing temperature (850℃) for sufficient densification thanconventional furnace sintering (950℃). Furthermore, MWS-derived specimens showed better electricfield-induced strain than that of CFS-derived specimens by effectively suppressing interdiffusions betweenceramic and electrode layers.