The effects of anti-ferroelectric nanofillers on the negative electrocaloric effects in Poly(vinylidene fluoride-trifluoroethylene) matrix composites

摘要

The electrocaloric effects (ECE) in the composites consisting of ferroelectric (FE) copolymer poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) and (Bi0.5Na0.5)TiO3-xBaTiO(3) nanoparticles (BNT-xBT, x = 0, 0.06, 1.0) are investigated. The anti-ferroelectric (AFE) nanofillers are found to affect more significantly than the FE nanofillers on the order-to-disorder phase transition near 60 degrees C in the copolymer matrix, as revealed by differential scanning calorimetry. Nevertheless, the influences of AFE nanofillers on the negative ECE are much weaker than that of FE nanofillers, suggesting that the negative ECE observed might not be associated with the AFE states in the composites. Instead, based on the dynamic mechanical analyses on the effects of nanofillers on the order-to-disorder phase transition in the copolymer matrix, the structural glassy states induced by the interaction between the nanofillers and the copolymer matrix are proposed to account for the negative ECE in the composite. This work provides an effective approach in enhancing the negative ECE, which is of technological importance to the implementation of electrocaloric refrigeration.