Structure and Ferroelectric Properties of High T_c BiScO₃-PbTiO₃ Epitaxial Thin Films

Piezoelectric ceramics of new composition with higher Curie temperature T_c are extensively studied for better piezoelectric microelectromechanical systems (MEMS). Apart from the compositional research, enhanced T_c could be achieved in a modified structure. We have considered that a designed laminated structure of Pb(Zr, Ti)O₃ (PZT)-based thin film, i.e., relaxed heteroepitaxial epitaxial thin film, is one of the promising modified structures to enhance T_c. This structure exhibits an extraordinarily high T_c, i.e., T_c ∼ 600 °C (bulk T_c∼ 365 °C). In this paper, we have fabricated the designed laminated structure of high T_c (1-x)BiScO₃-xPbTiO₃. T_c of BS-0.8PT thin films was found to be extraordinarily high, i.e., T_c∼ 750 °C (bulk T_c, ∼ 500 °C). Their ferroelectric performances were comparable to those of PZT-based thin films. The present BS-xPT thin films have a high potential for fabrication of high-temperature-stable piezoelectric MEMS. The mechanism of the enhanced T_c is probably the presence of the mechanically stable interface to temperature in the laminated structure. We believe this designed laminated structure can extract fruitful properties of bulk ferroelectric ceramics.