Enhanced electrocaloric effect in a Ba(1-x)SrxTiO3 compositionally graded film

An enhanced electrocaloric (EC) effect is observed in a 300 nm compositionally graded Ba(1-x)SrxTiO3 (BST) film prepared by a sol-gel method. It is found that the maximum EC effect in the compositionally graded films is much larger than that in the uniform film with the same thickness and external field. We infer that the enhanced EC effect is attributed to internal strains and space charge accumulation existing at the interfaces of the compositionally graded film. A thermodynamic model is developed to investigate our deduction, and the results are in agreement with the experimental results.