Development of novel Pb, Li, Na and K-free piezoelectric materials for Si-based MEMS application

We developed the piezoelectric materials not including Pb, Li, K and Na as constituent elements. Our concern is the composition survey of the morphotropic phase boundary between tetragonal and non-tetragonal ferroelectric materials. In this approach, we must select the tetragonal ferroelectrics other than PbTiO₃ and (Bi_1/2K_1/2)TiO₃ as a end material. BiCoO₃ and Bi(Zn_1/2Ti_1/2)O₃ are novel tetragonal candidates for this purpose. We successfully grew epitaxial tetragonal films having ferroelectricity in BiCoO₃-BiFeO₃ and Bi(Zn_1/2Ti_1/2)O₃-BiFeO₃ systems. Based on these system, composition having maximum piezoelectric response of d_33(AFM) = 280 pm/V was discovered for epitaxial films in Bi(Zn_1/2Ti_1/2)O₃-Bi(Mg_1/2Ti_1/2)O₃-BiFeO₃ system.