Large Transverse Piezoelectricity in Strained (Na,Bi)TiO₃–BaTiO₃Epitaxial Thin Films on MgO(110)

Abstract

Large transverse piezoelectricity has been demonstrated in lead-free epitaxial (Na,Bi)TiO3–BaTiO3 (NBT–BT) thin films grown on MgO(110) substrates. Through the internal strain caused by the difference in thermal expansion between NBT–BT and MgO, the crystal structure of the films was distorted to orthorhombic lattice, which does not form in bulk NBT–BT. The films showed a planar anisotropic nature where the effective transverse piezoelectricity along the orthorhombic b-axis was much larger than that along the orthorhombic a-axis. For the NBT–BT film with 9% BaTiO3, transverse piezoelectric coefficient d31* along the orthorhombic b-axis reached as high as -221 pC/N.