Abstract
Temperature stability of dielectric, ferroelectric, and piezoelectric properties were investigated in situ by choosing (K,Na)NbO3-(Bi,K)ZrO3 (KNN-BKZ), (K,Na)NbO3-(Bi,Na,K,Li)ZrO3 (KNN-BNKLZ), and (K,Na)NbO3-(Bi,Li)ZrO3-(KNN-BLZ) as representative ceramics with rhombohedral-orthorhombic-tetragonal (R-O-T), R-T, and enriched T phase boundaries, respectively. The KNN-BNKLZ ceramics, which have an R-T phase boundary, showed the highest piezoelectricity but the worst temperature stability. On the other hand, the KNN-BLZ ceramics, which have an enriched T-phase, were slightly worse in terms of piezoelectricity compared to the R-O-T or R-T phase boundary, but their thermal stability was the best. From analyses of an extrinsic contribution by a difference between the small signal d33 and εrPr and an intensity variation of the (002) and (200) X-ray diffraction peaks for the KNN-based ceramics, it was suggested that increasing the extrinsic contribution in the morphotropic phase boundary region improves the piezoelectricity but decreases the thermal stability.