Shear-Mode Piezoelectric Properties of Modified-(K,Na)NbO3 Ceramics for Hard Lead-Free Materials

(K0.45Na0.55)NbO3-0.5 mol% K4CuNb8O23 [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 K11T 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 (To-t similar to 200 degrees 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.