Study On The Electrocaloric Effect In PLZT Ferroelectric Ceramics And Programming Process Of Electrocaloric Data

Electrocaloric refrigeration,as a new generation refrigeration technology catered to energy conservation and environmental protection,has unparalleled advantages in many fields such as:energy utilization,operational reliability,refrigeration cost per unit area and application scenarios compared with traditional gas compression refrigeration.Therefore electrocaloric refrigeration is expected to play an important role in future refrigeration field.Nevertheless,the existing electrocaloric materials have many disad-vantages,which limit their practical application.The manufacturing process of ferroe-lectric ceramics is mature and its cost of production is low,but its breakdown strength is low;Polymer film can withstand extremely high electric field,but the amount of heat transferred from the load to the atmosphere is limited in a single cycle owing to its limited volume.In a word,whether electrocaloric materials has value in practical ap-plication or not is bound up with its electrocaloric performance near room temperature and refrigerating capacity.Electrocaloric performance is strongly dependent on its breakdown strength.Ceramics with excellent breakdown strength usually has excellent microscopic morphology such as:finer and uniform grains,uniform grain size and less pores in the grain gap in ceramics Therefore,it will be of great significance for the practical application of electrocaloric ceramic materials to improve the micro-structure of ceramics,increase its density,and optimize the breakdown strength characteristics.In this paper,the conventional solid-state reaction route was adopted to synthesize Pb_0.91La_0.09(Zr_0.65Ti_0.35)O_3.045 ferroelectric ceramics samples doped with different weight concentration（0wt%,1wt%,2wt%,3wt%,5wt%）of glass composed of different ratio of lead oxide to boron oxide,and a systematic study of microscopic morphology,electrical properties and electrocaloric performance has been carried out respectively.In order to optimize the surface morphology of ceramics by seeking the most appropri-ate weight concentration and most appropriate proportion of lead oxide to boron oxide,we analyze the differences between the results,and try to find the reason ac-counts for the differences.We have discovered that the PLZT ferroelectric ceramics samples without existing glass phase shows adiabatic temperature change△T=1.305K,isothermal entropy△S=1.483J/（kg·K）,the maximum grain size is about 4.56μm,the minimum size is0.87μm,the average size is 2.38μm,the breakdown field strength is about 90k V/cm.the electrocaloric performance leaves much to be desired due to the bad micro-mor-phology,including large great difference in grain size and insufficient uniformity of grains.After adding 2wt%boron-lead glass phase with a ratio of 1:0.6（mol%）to the ceramics,we find that the electrocaloric effects are optimized as△T=2.322K,△S=2.561J/（kg·K）,and the maximum grain size is 2.07μm,the minimum size is 0.56μm,the average size is 1.18μm,and the breakdown field strength is about 110k V/cm.It conclude that a proper amount of glass phase can optimize the microscopic morphology of ceramics,and improve its electrocaloric performance.In addition,it is necessary for us to deal with experimental data by software Origin.However,it seems that it is time-consuming for Origin to manipulate a large amount of data,especially the electrocaloric data.This article has written a program specifically for electrocaloric data processing in java to get rid of tediousness and inconvenience caused by the Origin.The program receives（Ti,Pj,Ek）data entered by the user in a tabular form with feature of simpleness,convenience and a certain degree of fault tol-eration.Users are not prone to make mistakes when they are entering data.Even if the user enters data with a mistake with carelessness,the program can prompt the user’s attention in time.The program can output two dimensional（2D）adiabatic temperature change（△Ti,Tj）discrete point set and 2D isothermal entropy change（△Si,Tj）discrete point set and other data on condition that any 3D discrete point set（Ti,Pj,Ek）infor-mation that supports 2D and any specified fitting number are both given.Meanwhile,the polarization point differential（d Pi/d Ti,Tj）discrete point set,and the intermediate data such as the fitting polynomial set under each electric field will be also generated together.And each result is highly consistent with the result calculated by Origin,and allows the user to save the result to the specified path.