Piezoelectric and pyroelectric properties of (001) oriented KNbO3 film

Abstract A phenomenological Landau-Devonshire theory is used to investigate the “misfit strain-temperature” phase diagram and physical properties of (001) oriented KNbO 3 film. Three ferroelectric phases, such as c phase, aa phase, and γ phase, occur in the phase diagram. In-plane compressive misfit strain is beneficial to form c phase and tensile strain makes aa phase stable. Physical properties of KNbO 3 film largely depend on misfit strain and electric field. At room temperature, γ phase of KNbO 3 film with the tensile misfit strain has larger piezoelectric and pyroelectric coefficients than that of c phase with the compressive strain. Large piezoelectric and pyroelectric coefficients are 180 pm/V and 8.5 × 10 −4  C/m 2 K respectively at the electric field of 100 KV/cm and misfit strain of 6.7 × 10 −3 , which are comparable with the experimental results of Pb(Zr x Ti 1− x )O 3 film. Therefore, choosing the appropriate substrates can be used to improve the physical properties of KNbO 3 film. In addition, the applied electric field decreases the dielectric, piezoelectric and pyroelectric properties of (001) oriented KNbO 3 film.