Synthesis and Characterisation of La doped PZT ceramics for potential Electrocaloric Cooling applications

Abstract

Over the last century, the vapor compression and expansion cycle has been the most widely used technique for refrigeration and other cooling applications. This technique uses gases like chlorofluorocarbons and hydrofluorocarbons as refrigerants, which are majorly responsible for the depletion of the ozone layer and are potent greenhouse gases. There has been a growing concern over the effects of ozone layer depletion and global warming, thereby pressuring the refrigeration industry to look for alternative cooling technologies which are more environment-friendly as well as energy efficient. This has brought solid-state cooling, especially electrocaloric cooling into the limelight which is based on the electrocaloric effect. The electrocaloric (EC) effect is the temperature change caused by the change in electric field intensity of a thermally isolated system. Even though the EC effect was first discovered in 1930 in Rochelle Salt, EC cooling has only resurged recently with the discovery of large EC temperature changes of 12 ⁰C in Lead Zirconate Titanate and poly(vinylidene fluoridetrifluoroethylene) [P(VDFTrFE)] ferroelectric thin-films. This thesis investigates the properties of Lead Zirconate Titanate (PZT) and Lanthanum doped Lead Zirconate Titanate (PLZT) ceramics as potential candidates for electrocaloric cooling applications at room temperature. The materials are synthesized using the conventional solid-state method and characterized using different techniques such as powder X-ray diffraction at different temperatures, TGA, DSC, and dielectric measurements. The effect of doping Lanthanum in different amounts on the structural and dielectric properties of Lead Zirconate Titanate is studied in detail.