The enhanced electrocaloric effect in P(VDF-TrFE) copolymer with barium strontium titanate nano-fillers synthesized via an effective hydrothermal method

Abstract

An effective hydrothermal method is developed to synthesize barium strontium titanate (BST) nanoparticles with a mean size below 30 nm, which are used for the fabrication of nanocomposite films consisting of ferroelectric co-polymer poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) and ceramic nanoparticles. The interface between the nanoparticle and the polymeric matrix is found to improve the polarization and pyroelectric behaviors of the nanocomposites, resulting in a much enhanced electrocaloric effect as compared with that of the pristine P(VDF-TrFE). The electrocaloric temperature change is 2.5 °C under electric fields of ∼600 kV cm⁻¹. The effects of Ba_0.75Sr_0.25TiO₃ nanoparticles on the ferroelectric-to-paraelectric transition of P(VDF-TrFE) are investigated using dynamical mechanical relaxation. The results suggest that the improved electrocaloric effect in the nanocomposites could be related with the localized polarization field near the surfaces of Ba_0.75Sr_0.25TiO₃ nanoparticles.