Influence of thermal stresses on the electrocaloric properties of ferroelectric films

A nonlinear thermodynamic theory is used to analyze the influence of thermal stresses on electrocaloric (EC) properties of (001)-textured polycrystalline monodomain BaTiO3, Ba0.6Sr0.4TiO3, and PbTiO3 films on integrated circuit-compatible substrates Si, c-sapphire, and a-sapphire. The results show that the EC response can depend strongly on the film growth temperature T-G which can shift the maximum in EC properties to a working temperature of interest. For BaTiO3 films on Si, the thermal stresses are sufficient to shift the zero-field Curie temperature T-C near to room temperature, resulting in a strong enhancement of the EC properties as compared to the bulk material. (C) 2011 American Institute of Physics. [doi:10.1063/1.3573788]