Stabilization of the relaxor phase by adding CuO in lead-free (Bi1/2Na1/2)TiO3‒SrTiO3‒BiFeO3 ceramics

We investigated microstructures, crystal structures, and electrical properties of high temperature sintered (1‒x)BiNaTiO3‒xSrTiO3‒2BiFeO3 (BNST100x‒2BF, x = 0.20 and 0.22) ceramics without added CuO and compared these results with low temperature sintered BNST100x‒2BF ceramics with 1 mol% of added CuO. The sintering temperature and average grain size of BNST100x‒2BF ceramics decreased after addition of CuO. We found that changes in the stabilized relaxor phase with decreasing sintering temperature resulted in changes in the temperature dependent dielectric properties and provided the enhanced electromechanical strain properties in BNST100x‒2BF ceramics. Therefore, we suggest that the nonergodicity to ergodicity transition is able to induce by changes in sintering temperature with added CuO and this result is important to tailor the electrical properties of BNT‒based lead‒free ceramics in proceeding with practical application.