Effect of rare earth Er and Dy on the Curie temperature and interfacial charge mobility of electrocaloric PVDF-HFP composites

Nowadays, ferroelectric polymer composites are desirable for novel electrocaloric cooling technology. Ferroelectric poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) thin films with the different electronegativity (EN) rare earth fillers Erbium (Er) and Dysprosium (Dy) have been studied in this work. Solution casting method was used to fabricate the thin films. The electroactive β phase on both crystalline and amorphous regions of PVDF-HFP was intensified by this filler. However, the stronger EN filler Er induced the β phase on crystalline region more strongly than Dy, resulting in total crystalline region reduction along with dielectric constant. On increasing the filler loading, the Curie temperature decreased dramatically by 40 °C with decreasing maximum negative temperature change (∆Tmax). The best performance in the Curie temperature reduction was found with 1 wt% Er filler. This reduced the Curie temperature and increased the dielectric constant related with micro-phase structure and interfacial charge mobility that will be discussed for future electrocaloric cooling applications.