Modified (K0.5Na0.5)NbO3 based lead-free piezoelectrics with broad temperature usage range

(K0.5Na0.5)NbO3 (KNN) based lead-free materials exhibit arguably, comparable piezoelectric properties to conventional Pb(Zr,Ti)O-3 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 BaTiO3 based piezoelectrics, the addition of CaTiO3 in KNN materials was found to shift the TO-T well below room temperature. Piezoelectric and electromechanical values of KNN-LiSbO3-CaTiO3 material were found to be d(33)similar to 210 pC/N, d(15)similar to 268 pC/N and k(33)similar to 61%, k(15)similar to 56%, respectively, with greatly improved temperature stability over the temperature range of -50-200 degrees C, demonstrating practical potential for actuator and/or ultrasonic transducer applications. (C) 2007 American Institute of Physics.