Study On Modifing And Mechanism Of BCZT-Based Lead-Free Piezoelectric Ceramics

Piezoelectric ceramics can realize the conversion between electrical energy and mechanical energy,so that they have been widely used in many fields.At present,Lead-zirconate titanate piezoelectric ceramics,which are currently the most widely used in the market.The excessive lead content makes PZT cause great harm to the environment and human body during the manufacturing and use process.Therefore,research on lead-free piezoelectric materials has become necessary.In recent years,major breakthroughs have been made in the research of lead-free piezoelectric materials,but its electrical performance is still incomparable with lead-based piezoelectric materials.Therefore,this article use(Ba_0.99Ca_0.01)(Zr_0.02Ti_0.98)O₃（BCZT）as the understructure,through doping modification and improving the preparation process to enhance its electrical properties.And analyzed the relationship between its phase composition,microscopic morphology,etc.and electrical properties of piezoelectric materials.The main research content is as follows:1.The BCZT based lead-free piezoelectric ceramics doped with LiTaO₃ were prepared by the conventional solid-phase method,and the doping content was x=0～0.2%.The influence of microstructure,phase structure,electrical performance with doping LiTaO₃ on BCZT-based piezoelectric ceramics was studied.The research results show that BCZT-LT presents a single perovskite structure,combined with the analysis of the dielectric temperature spectrum,it can be seen that the ceramic samples have multi-phase coexistence.Because the addition of a small amount of LiTaO₃ will increase the grain size and improve the density of the ceramic,it plays a role in improving the ferroelectric,piezoelectric and dielectric properties of BCZT-based piezoelectric ceramics.When the amount of LiTaO₃ is 0.1%,the Curie temperature remains at 129℃,the P_r～16.6μC/cm² is increased by 6.9μC/cm² compared with the undoped piezoelectric ceramics,and the piezoelectric constant is increased by about 120p C/N.2.The piezoelectric ceramic BCZT-xEu₂O₃（x=0,0.05,0.1,0.15,0.2%）was prepared by solid-phase method.Through research,it is found that different doping amounts of Eu₂O₃have significant effect on the microstructure,phase structure,dielectric properties,ferroelectric properties and piezoelectric properties of BCZT.The doping of Eu₂O₃ will increase the concentration of oxygen vacancies in the ceramic,significantly reduced the mean size of crystal grains,reduce the number of pores,and densify the sample,thereby increasing the electrical properties of the ceramic sample.The research results show that the ceramics sample has the best electrical properties when the sintering temperature is 1410℃and x=0.2%.The piezoelectric constant of the doped piezoelectric ceramic has increased by about 140p C/N,d₃₃～389p C/N;When x=0.05%,the highest energy storage density and energy storage efficiencyη～61.76%are obtained.3.The effects of co-doping LiTaO₃ and Eu₂O₃in BCZT-based piezoelectric ceramics on the phase structure,microscopic morphology and electrical properties of lead-free piezoelectric ceramics are studied.The results show that the joint action of LiTaO₃and Eu₂O₃can greatly reduce the sintering temperature of BCZT-based piezoelectric ceramics.At this time,the ceramic sample has a single perovskite structure and multiple phases coexist,and the proportion of tetragonal phases gradually increases with the increase of temperature.According to the electrical performance analysis,the best electrical performance is obtained when the doping amount of LiTaO₃ is 0.04%,the doping ratio of Eu₂O₃ is 0.15%and the sintering temperature is 1370℃.At this time,the piezoelectric constant has increased by about 146p C/N,andε_r has increased by about 36%compared to the undoped piezoelectric ceramic.Through the analysis of the dielectric test results,it can be seen that the Curie temperature T_C of the piezoelectric ceramic has increased from 125℃to 134.2℃,and the phase transition temperature T_O-T～21.2℃.