Strain-driven control of piezoelectricity in (Na,Bi)TiO3-BaTiO3 epitaxial thin films.

Thermal strain effect on the piezoelectricity was investigated for (Na,Bi)TiO3-BaTiO3 (NBT-BT) thin films on various substrates with (100) and (110) orientations. The compressive-thermal strain caused an increase in the remnant polarization unaccompanied by a decrease in dielectric permittivity, which resulted in enhancement of the piezoelectric coefficient, e*31. For films on (110) substrates, the crystal lattices were distorted to orthorhombic symmetry under both the tensile- and compressive-strains and the in-plane anisotropy of piezoelectricity emerged with e*31 as large as -19 to -20.6 C/m2. We conclude that the large piezoelectricity in NBT-BT films on (110) substrates is related to the appearance of orthorhombic phase. [ABSTRACT FROM AUTHOR]