Low temperature sintering of lead–free (Bi1/2Na1/2)TiO3-SrTiO3-BiFeO3 piezoelectric ceramics by adding excess CuO

This study examined the microstructures, crystal structures, and electrical properties of 0.01 mol CuO–added (1–x)(Bi1/2Na1/2)TiO3–xSrTiO3–2BiFeO3 (BNST100x–2BF, x = 0.20 ~ 0.28) ceramics synthesized at two different sintering temperatures. The sintering temperature of the BNST100x–2BF ceramics could be decreased from 1175 °C to 1000 °C by adding a 0.01 mol CuO excess. Low–temperature sintering led to a decrease in average grain size. The dielectrics, polarization hysteresis (P–E), switching current, and electric–field induced strain (S–E) curves changed with increasing SrTiO3 content and decreasing sintering temperature. Interestingly, the highest reduction ratio of d33* was calculated to be somewhere in between the high–temperature sintered and low–temperature sintered BNST26–2BF ceramics. These results were attributed to the difference in the stabilized relaxor state and closely related to the electric field–induced reversible phase transition from the relaxor and ferroelectrics.