The effects of additions of two-dimensional graphitic-CN on the negative electro-caloric effects in P(VDF-TrFE) copolymers.

In order to enhance and tune the electrocaloric effect (ECE) and ferroelectric responses, nanocomposites containing ferroelectric copolymer poly(vinylidene fluoride trifluoroethylene) and two-dimensional (2D) graphitic-CN (g-CN) are synthesized. The effects of g-CN on the ferroelectric-to-paraelectric phase transition of the copolymer are investigated by the differential scanning calorimetry (DSC), P-E hysteresis loop and dielectric spectrum measurements. The results indicate that the addition of 2D g-CN in the ferroelectric copolymer is an effective approach in enhancing its dielectric and ferroelectric properties. Furthermore, the nanocomposites show the maximum absolute value of negative electrocaloric effect (ECE) of 5.4 K at 322 K under an electric field of 0.45 MV cm, which is much better than that of pristine copolymer. The negative ECE of the nanocomposites can be well explained by the Kauzmann theory. The low cost and enhanced negative ferroelectric properties of P(VDF-TrFE) make them more feasible over ceramics materials such as lead zirconate titanate (PZT) based ferroelectrics for applications in electrocaloric refrigeration.