Dielectric behavior of ferroelectric thin films grown on orthorhombic substrates

Using Landau–Devonshire (LD)-type phenomenological model, we investigate the dielectric behaviors of single-domain PT thin films grown on orthorhombic substrates. Effects of in-plane misfit strains and external electric fields are combined on dielectric properties. In our calculation of permittivities, we take account of the susceptibility matrix. Basing on the assumption that in-plane misfit strains um1=−um2um1=−um2, we find that in-plane permittivities ε11ε11 and ε22ε22 are symmetrical about the line where in-plane misfit strains are zero. Same is out-plane permittivity ε33ε33. Anisotropic in-plane misfit strains result in anomalies of permittivities at boundaries of phase transitions. Further calculation reveals that dielectric tunability reach to maximums at boundaries of phase transitions where the same direction polarization component appears or disappears. So the permittivities and tunabilities can be chosen to satisfy different demands by controlling applied fields and changing in-plane misfit strains.