Excellent fatigue resistance in Sb nonstoichiometric KNN-based ceramics by engineering relaxor multiphase state

Abstract

Potassium sodium niobate (KNN)-based ceramics were considered to be a promising candidate for actuators, and the long-term reliability, as a major consideration in practical applications, should be given adequate attention. Here, lead-free KNN-based ceramics with antimony (Sb) nonstoichiometric have been designed to improve both the piezoelectricity and electric fatigue resistance. The variation of Sb not only benefits for the piezoelectricity, but also greatly affects their electric fatigue behaviors. That is, the ceramic with excess Sb has excellent fatigue resistance while the ceramic with deficient Sb has pronounced fatigue. This new phenomenon is attributed to the local polar-structure states: The relaxor multiphase coexistence state, reduced orthorhombic phase fraction and refined domain size in the ceramic with excess Sb, together contribute to the enhancement of fatigue resistance. We believe that the simple approach of Sb nonstoichiometric adjustment has provide an important route to simultaneously achieve excellent piezo-response and fatigue resistance.