Fabrication And Characterization Of Ferroelectric P(VDF-TrFE) Copolymer Thin Films

Refrigeration technology is a part of domestic and industrial applications which is absolutely necessary. vapor-compression cycle for refrigeration is common today, however one of the major disadvantages of this method are environmental concerns with most of the widely used refrigerants such as Freon that have been shown to contribute to depletion in the ozone layer. With the trend of environmental pollution control and the miniaturization of electronics, developing novel environmentally friendly cooling technologies is imperative subsequently. Compared with conventional principle of refrigeration, ferroelectric materials show the capability of refrigeration which is smaller and more environmental based on the electrocaloric effect. When an electric field is applied to a dielectric material, it will induce a change in the material’s polarization. The consequent changes in the entropy and/or temperature of the material are referred to as the electrocaloric effect (ECE). This effect makes ferroelectric materials have a huge potential for utilizing this effect for solid state cooling.This study take the normal ferroelectric poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] (55/45 mol.%) copolymer as research object, the background section first covers the fundamentals of the ECE and advancements that have been made over the years on ferroelectric materials. Then the microstructure and crystallinity of the P(VDF-TrFE) film have been investigated comprehensively by using X-ray diffractometer (XRD), scanning electron microscope(SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis(TGA). The selection of solvent, rotating speed of spin-coating, temperature of condition when spin-coat and the temperature of annealing is discussed along with the P(VDF-TrFE) films to choose the best experiment parameters. It proves that DMF is the most suitable solvent, and when the rotating speed is 2000rpm, spin-coat at lower temperature and anneal at 140℃, the best microstructure and crystallinity can be obtained.The characterization study of P(VDF-TrFE) film is in the last chapter. The result of Nano tensile test indicated that the film annealing at 140℃ has the largest Young’s modulus due to the best crystallinity. The electrocaloric entropy change electrocaloric temperature change (△T) is calculated by measured hysteresis loops of P(VDF-TrFE) thin films at various temperatures. It is the highest in P(VDF-TrFE) film where by operating at higher electric field and 110℃, when △T can reach 12.13℃. Then direct measurement of the refrigeration by P(VDF-TrFE) films was carried out by using a infrared thermometer, which indicated that P(VDF-TrFE) films have considerable refrigeration capability and the effect became better with the increase of strength of the electric field in a certain range.