Preparation Of High Performance Lead-Free Piezoelectric Ceramics

PZT series ceramics are widely used due to their excellent performance.However,the development of environment friendly materials has made the development of lead-free piezoelectric new materials extremely urgent.BiFeO₃ is currently known the only multiferroic material that have an antiferromagnetic order and a ferroelectric sequence?T_C=830??at room temperature.However,its single-phase preparation is difficult,high loss and large leakage current,and spin-cycloidal modulation structure make BiFeO₃ seriously restricted in studying magnetoelectric performance.our research group has clarified the mechanism of difficult preparation and high loss of BiFeO₃ single phase,and produced a single-phase low-loss BiFeO₃-based ternary solid solution.At the same time,our research group obtained phase diagram of BiFeO₃-Bi(Zn_1/2Ti_1/2)O₃-BaTiO₃?BF-BZT-BT?by data integration.The structural phase boundary in the phase diagram expands from point of binary system to line of ternary system,and can adjust the electrical properties in a larger range of compositions.In this paper,BiFeO₃-based ferroelectric material was designed and prepared to obtain high electrical resistivity and low-loss materials.1.Preparation and piezoelectric properties of BF-BZT-BT ceramics with compositions near the R-PC structural phase boundary.According to BF-BZT-BT ternary structure phase diagram,several compositions located near phase boundary were prepared by a refined solid phase reaction electronic ceramic process design.The structure test shows that the sample structure is trigonal-pseudocubic phase near trigonal phase boundary.BF69-BZT4-BT27+0.17%wtMnO₂ electrical testing performance parameters:tan?=0.027?d₃₃=146pC/N?T_C=527?,BF69-BZT4-BT27+0.17%wtMnO₂ and BF67-BZT4-BT29+0.8%molMnO₂mass ratio of 1:1 electrical testing performance parameters:tan?=0.029?d₃₃=140pC/N?T_C=527?.Time and temperature aging tests get good results,BF69-BZT4-BT27+0.17%wtMnO₂ compositions piezoelectric constant drop below 10%after 90 days,sample temperature aging test shows that most of the material can be used at 300? stablly.In addition,it was found that there were significant differences in sample properties under the same preparation conditions,mainly due to the instability of manual powder.It is found that the comprehensive properties of some ceramics have exceeded the current commercial lead metabobate piezoelectric ceramics K-81(tan?=0.01?d₃₃=85pC/N?T_C=460?).2.Preparation and piezoelectric properties of BF-BZT-BT ceramics with compositions far away the R-PC structural phase boundary.Some of BF-BZT-BT compositions far from phase boundary were designed and prepared by refined solid phase reaction electronic ceramic technology.The structure test shows that the prepared samples phase boundary is trigonal phase structure.Electrical performance tests BF75-BZT3-BT22+0.9%molMnO₂ compositions show the excellent performance,tan?=0.007?d₃₃=78pC/N?T_C=588?.The piezoelectric constants of the three samples of compositions BF74.7-BZT2.5-BT22.8+0.7%molMnO₂ showed no difference under the conditions of 5kV/mm,6kV/mm and 7kV/mm.It can be seen that the piezoelectric constants were not significantly improved by increasing the poling electric field strength when the material preparation was confirmed.In addition,the dielectric temperature spectrum results of different manganese doped BF75-BZT3-BT22 samples showed that the Curie temperature was different.According to the analysis,the Curie temperature of the material was decreased by 0.9%molMnO₂ compared with 0.7%molMnO₂ doping.Thermal aging stability test results show that the BF75-BZT3-BT22+0.9%molMnO₂ material can be use normally at 300?.The electromechanical coupling coefficient,frequency constant and reflection absorption of some samples were tested to provide reference for understanding the different properties of materials.The comprehensive properties of some excellent ceramics have exceeded the current commercial application of bismuth titanate series ceramics K-15(tan?=0.03?d₃₃=18pC/N?T_C=600?).