Study On The Structure And Dielectric Properties Of High Entropy Perovskite Ceramics（LaLiBaSrCa）TiO₃

With the advancement of science and technology,the demand for new materials is increasingly urgent.Therefore,materials science is facing a huge challenge to continuously develop new materials with excellent properties.In recent years,the advent of high-entropy alloys has provided new ideas and new methods for the development of new materials.Prior to 2015,research on high-entropy materials focused on metallic materials.In 2015,Rost and his collaborators proposed the concept of high-entropy ceramics(oxides).Since the concept of high-entropy ceramics has appeared,it has been widely studied and discussed by scholars at home and abroad,and some research results have been obtained.For traditional materials,there is still a lack of clear understanding of many basic scientific issues involved in high-entropy ceramics.There are relatively few theoretical and experimental studies,especially the theory is basically borrowed from high-entropy alloys.Generally speaking,high-entropy ceramics It is still in its infancy,and its related researches are mainly focused on the rock salt structure(Mg0.2Co0.2Ni0.2Cu0.2Zn0.2)O and its derived materials discovered by Rost,while the ABO3 type perovskite structure with rich physical connotation is high.Entropy ceramics is rarely studied.Therefore,there is an urgent need for research on A-site high-entropy perovskite ceramics.In this paper,solid phase sintering method was used to successfully prepare a high-entropy ceramic with a molar ratio of A site—(La0.2Li0.2Ba0.2Sr0.2Ca0.2)TiO3.The high-entropy ceramics were analyzed by XRD,SEM and TEM.The results show that the ceramic has a cubic perovskite structure and has a preferred orientation.The dielectric test results show that when the sintering temperature is 1350℃,the maximum dielectric constant appears.When the frequency is 100 Hz,the value of the dielectric constant is 230,and the dielectric loss is 0.11.In order to further optimize the performance of ceramics and consider the valence compensation mechanism,the content of La and Li in(La0.5Li0.5)x(Ba1/3Sr1/3Ca1/3)(1-x)TiO3(that is,adjusted the value of x is 0.1,0.2,0.3,0.4,0.5,0.6,0.7,respectively)to prepare 7 high-entropy perovskite ceramics whose components change sequentially.Analysis shows that these seven ceramics have cubic perovskite structure and all have preferred orientation.The dielectric test results show that as x increases,the maximum value of the dielectric constant of the ceramic shifts toward a lower sintering temperature,which is caused by the ceramic grain size effect,and the ceramic has an optimal dielectric The constant grain size ranges from 1.63 μm to 2.98 μm.Therefore,the high entropy ceramics can control the size of the grain size by adjusting its sintering temperature and La and Li content,thereby further achieving controllability of the dielectric properties.In addition,the dielectric constant of x=0.7 ceramic sample does not have a uniform change with the sintering temperature,and its dielectric constant and dielectric loss show a sharp increase compared to the first 6 groups of ceramic samples.When the junction temperature is 1400℃ When the frequency is 100 Hz,the dielectric constant can reach 28958.