Design of p‐type NKN‐based piezoelectric ceramics sintered in low oxygen partial pressure by defect engineering

Abstract

AbstractThe reduction‐resistant properties of piezoelectric ceramics are of great importance for multilayer monolithic structures based on base metal inner electrodes, particularly for recently reported niobate‐based lead‐free perovskites. In this letter, the Hall‐effect measurement and impedance analysis indicate that conventional (K,Na)NbO3 (NKN)‐based ceramics exhibit an n‐type electronic conduction. Rapid increase in the concentrations of oxygen vacancies and electrons is responsible for severe degradation of resistivity and piezoelectric properties as sintered in N2. By comparison, p‐type NKN‐based ceramics by Mn doping exhibit excellent electrical properties (d33 = 368 pC/N, = 643 pm/V, tanδ = 0.019, and IR = 39.9 GΩ · cm) in N2 sintering atmosphere, as well interpreted by a series of proposed defect chemistry equations. The experimental results suggest that an introduction of the p‐type conduction behavior should be an effective strategy to enabling NKN‐based ceramics and Cu/Ni electrodes to well co‐fire in a weakly reducing atmosphere.