Modified (K0.5 Na0.5) Nb O3 based lead-free piezoelectrics with broad temperature usage range

Abstract

(K0.5 Na0.5) Nb O3 (KNN) based lead-free materials exhibit arguably, comparable piezoelectric properties to conventional Pb (Zr,Ti) O3 ceramics owing to an orthorhombic to tetragonal polymorphic phase transition (TO-T) occurring near room temperature. However, this transition correspondingly results in a strong temperature dependence of the dielectric and piezoelectric properties, being limited further by domain instability, during thermal cycling between the two ferroelectric phases. Analogous to BaTi O3 based piezoelectrics, the addition of CaTi O3 in KNN materials was found to shift the TO-T well below room temperature. Piezoelectric and electromechanical values of KNN-LiSb O3 -CaTi O3 material were found to be d33 ∼210 pCN, d15 ∼268 pCN and k33 ∼61%, k15 ∼56%, respectively, with greatly improved temperature stability over the temperature range of -50-200 °C, demonstrating practical potential for actuator and/or ultrasonic transducer applications. © 2007 American Institute of Physics.