Abstract
The measured dielectric constant as a function of electric field, at a frequency of 1MHz is reported for sol-gel deposited Barium-Strontium Titanate (BaxSr1–x TiO3) thin films with x = 0.0 to 0.6 at different temperatures and film thicknesses. The experimental data can be explained by Devonshire thermodynamic theory of free energy expansion in terms of power series of polarization. It is shown that the expansion upto the quadratic term is sufficient to explain the field dependence of dielectric constant. The coefficient C3 of the quadratic term is almost independent of electric field, thickness and temperature but appears to depend on composition and mechanical strains. The effect of strains on C3 shows that the electrostrictive coefficients Q 11, Q 12 and the elastic constants c 11 and c 12 are different in thin films with respect to the bulk.