Effect of Mechanical Boundary Conditions and Thermal Stresses on the Electrocaloric and Pyroelectric Properties of Ferroelectric Films

We use a non-linear thermodynamic model to describe quantitatively the electrothermal response of perovskite ferroelectric thin films under different electrical, thermal and mechanical boundary conditions. A comparison of ferroelectric materials such as BaTiO$_{3}$, PbTiO$_{3}$, and SrTiO$_{3}$ illustrates the influence of composition and lateral clamping effect on the electrocaloric properties. The theoretical analysis of a variety of (001)-textured polycrystalline ferroelectric thin films on IC-friendly substrates such as Si and sapphire shows that the thermal stresses that develop during processing shift the zero-field Curie temperature, and have a significant influence on the pyroelectric properties of thin film ferroelectric materials. We also demonstrate that the maximum in the electrocaloric properties can be shifted to a working temperature of interest by adjusting the deposition/processing temperature. These results provide insights on how to optimize pyroelectric and electrocaloric properties.