Role of sintering temperature in tailoring the electrical properties of 0.98KNNS–0.02BNZSH piezoelectric ceramics

Lead-free 0.98(K0.5Na0.5)(Nb0.96Sb0.04O3)–0.02(Bi0.5Na0.5)(Zr0.8Sn0.1Hf0.1)O3 (0.98KNNS–0.02BNZSH) perovskite ferroelectric ceramics have been designed and prepared through the traditional ceramic fabrication technique. To have an insight on the effects of sintering temperature (in the range from 1020 to 1110 °C), the structural, microstructural, dielectric and ferro/piezoelectric properties of 0.98KNNS–0.02BNZSH ceramics are investigated systematically. The structural analysis has revealed a pure perovskite phase for sintering at different temperatures. The rhombohedral (R) and orthorhombic (O) phases coexist for sintering of 0.98KNNS–0.02BNZSH ceramic at 1080 °C, while the rhombohedral phase dominates above 1080 °C. The grains become more uniform and tightly packed when the sintering temperature is increased from 1020 to 1080 °C. However, the grain size and the density have been revealed to be decreased for samples sintered above 1080 °C. The conduction behavior of 0.98KNNS–0.02BNZSH ceramics has also been investigated using complex impedance spectroscopy. The optimum values of different dielectric and ferro/piezoelectric parameters for 0.98KNNS–0.02BNZSH ceramics sintered at 1080 °C are obtained to be as the following: TC ~ 317 °C, εmax ~ 7102, tanδ ~ 0.10, ρ ~ 4.49 g/cm3, d33 ~ 180 pC/N, and Pr ~ 16.7 µC/cm2. These findings show that crystallizability, density, and electrical properties are significantly influenced by the sintering temperature.