Composition dependence of phase structure and electrical properties in (0.98-x)K0.35Na0.65NbO3-0.02BaZrO3-xBi0.5Na0.5ZrO3 ternary ceramics

In this study, we fabricated the ternary ceramic system of (0.98-x)K0.35Na0.65NbO3-0.02BaZrO3-xBi0.5Na0.5ZrO3 (KNN-BZ-BNZ-x) by the conventional solid-state method, and the composition dependence of their phase structure and electrical properties was studied in detail. These results indicate that the ceramics endure a series of phase transitions with increasing BNZ content, and then the rhombohedral-orthorhombic-tetragonal (R-O-T) phases coexistence can be established in the ceramics with 0.02 < x < 0.04, as confirmed by temperature-dependent dielectric constant as well as their XRD patterns. For the compositions with R-O-T phase boundary, the ceramics possess a higher dielectric constant (εr∼1980-2285) and a relatively large remanent polarization (Pr = 15.8-18.2 μC/cm2). Moreover, the ceramics with x = 0.025 exhibit a large piezoelectric constant (d33 = 345 pC/N) and a high kp (∼50%) because of the formation of R-O-T phase boundary as well as the enhancement in εr and Pr. As a result, the ceramic system is one of the most promising candidates in the field of lead-free high-temperature piezoelectrics.