Shear‐Mode Piezoelectric Properties of Modified‐(K,Na)NbO ₃ Ceramics for “Hard” Lead‐Free Materials

Abstract

(K 0.45 Na 0.55 )NbO 3 –0.5 mol% K 4 CuNb 8 O 23 [KNN–KCN] solid solution was synthesized and its shear mode dielectric and piezoelectric properties were characterized as a function of temperature. The doped KNN material was found to possess comparable electric resistivity, piezoelectric, and electromechanical properties with pure KNN, but with a much higher mechanical Q m value, being on the order of 1500. The dielectric permittivity K 11 T and piezoelectric coefficients d 15 for KNN–KCN were found to increase with the increasing temperature, while the electromechanical coupling factors k 15 maintain a similar value till the phase transition temperature ( T o − t ∼200°C), above which, the properties drop significantly due to depolarization. The good temperature‐dependent properties, together with its high mechanical Q m , demonstrate a practical potential of KNN–KCN materials for high power shear‐mode applications.