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 Qm value, being on the order of 1500. The dielectric permittivity K11T and piezoelectric coefficients d15 for KNN–KCN were found to increase with the increasing temperature, while the electromechanical coupling factors k15 maintain a similar value till the phase transition temperature (To−t∼200°C), above which, the properties drop significantly due to depolarization. The good temperature-dependent properties, together with its high mechanical Qm, demonstrate a practical potential of KNN–KCN materials for high power shear-mode applications.
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