Wiley, Journal of the American Ceramic Society, 8(91), p. 2716-2719, 2008
DOI: 10.1111/j.1551-2916.2008.02469.x
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Conventional sintering of (Na1−xKx)0.5Bi0.5TiO3 (abbreviated as NKBTx, x=18–22 mol%) lead-free piezoelectric ceramics was investigated to clarify the optimal sintering temperature for densification and electrical properties. Both sintered density and electrical properties were sensitive to sintering temperature; particularly, the piezoelectric properties deteriorated when the ceramics were sintered above the optimum temperature. The NKBT20 and NKBT22 ceramics synthesized at 1110°–1170°C showed a phase transition from tetragonal to rhombohedral symmetry, which was similar to the morphotropic phase boundary (MPB). Because of such MPB-like behavior, the highest piezoelectric constant (d33) of about 192 pC/N with a high electromechanical coupling factor (kp) of about 32% were obtained in the NKBT22 ceramics sintered at 1150°C.