Simultaneous increase in piezoelectric response and Curie point in BaTiO₃ based Pb-free piezoceramic

Piezoelectric ceramics are used in wide-ranging applications as actuators, transducers, and sensors. For applications at ambient environmental conditions, it is desirable that the piezoelectric material exhibit large piezoelectric coefficient (d(33)) and possess Curie point well above room temperature. Among the lead-free piezoelectrics, the classical ferroelectric BaTiO3 exhibits Curie point and d(33) similar to 120 degrees C and 190 pC/N, respectively. Most attempts at improving the d(33) of BaTiO3 via chemical modifications significantly reduces the Curie point (T-c). Here we show that it is possible to improve both the d(33) and T-c of BaTiO3. We found this possibility while investigating a solid solution of BaTiO3 with BaAlO2.5. An optimum composition, 0.97 BaTiO3-0.03BaAlO(2.5) of this solid solution exhibit d(33) similar to 356 pC/N, Curie point 125 degrees C, and good thermal stability of the piezo response