Effects of K4CuNb8O23 and GeO2 addition on microstructure and piezoelectric properties in KNbO3 ceramics

Abstract

Abstract A combined additives study of lead-free KNbO3 (KN) ceramics in the solid-state reaction was performed to improve the mechanical quality factor (Q m) for high power piezoelectric applications. Improved Q m values of 1137 and 1241 were confirmed in KN specimens with addition of 1.0 mol% K4CuNb8O23 (KCN) and 1.0 mol% KCN + 0.5 wt% GeO2, respectively. It is important for achievement of the higher Q m in KN systems to control the composition of the Cu segregated phase. In this study, the Cu segregated phase which was necessary to improve the Q m resulted from decomposition of the KCN compound during the sintering. Co-doping of KCN and GeO2 to KN specimens has a remarkable effect in suppressing the deliquescence accompanying KCN addition and improvement of the Q m without significant deterioration of the electromechanical coupling factor k 31.