Microstructure and electrical properties of lead free potassium sodium niobate piezoceramics with nano ZnO additive

Lead free potassium sodium niobate piezoelectric ceramics were synthesized through conventional mixed oxide method. Crystal structure and microstructure were analyzed by X-ray diffraction and scanning electron microscopy. The average grain size was calculated by using SEM photographs. The effects of nano ZnO additive as a nano scale sintering aid, on grain size and electrical properties of pure KNN and (K0.5Na0.5) (MoxTiyNb1−x−y)O3 ceramics were investigated. Our results reveal that nano ZnO alters the microstructure by increasing the average grain size at lower sintering temperature which improves the piezoelectric properties. The nano size ZnO additive shows significant difference on KNN microstructure over micro size ZnO additive. The optimum values of dielectric, piezoelectric and ferroelectric properties were obtained for KNN samples with 0.4–0.8 mol% nano ZnO additive sintered at 1030–1070 °C.