The dielectric behavior of polycrystalline ferroelectric films with fiber textures

We consider the effects of crystallographic symmetry, texture, and internal strain on the dielectric properties of polycrystalline ferroelectric thin films with fiber textures, including spontaneous polarization, coercivity, dielectric constant, dielectric tunability, and strain-induced phase transition, by combining Landau-Ginzburg-Devonshire phenomenological theory for ferroelectrics with the micromechanics theory for polycrystalline thin films. Cubic and tetragonal BaxSr1−xTiO3 (BST) films with [0 0 1] fiber texture, and cubic and rhombohedral BST films with [1 1 1] texture are considered. The results show that for [0 0 1]-textured film compressive strain enhances the spontaneous polarization, coercivity, and tunability while it decreases the dielectric constant; for [1 1 1]-textured film the effects are the opposite. It is also noted that [1 1 1]-textured films are less sensitive to internal strain than [0 0 1]-textured films. Good agreement with experimental data is also observed.