Study On BiScO₃-PbTiO₃ Based High Temperature Piezoelectric Ceramics And The Actuator

Multilayer piezoelectric ceramic actuators are a kind of driving device which use piezoelectric ceramics as the key materials.They are widely used in various fields such as commercial turbines,engines,and precision machine tools,to name a few.With the development of aerospace,petroleum and other industries,more and more requirements are imposed on the operating temperature of actuators.BiScO₃-PbTiO₃（BS-PT）piezoelectric ceramic exhibits excellent piezoelectric performance(d₃₃=460 p C/N,k_p=0.56)and high Curie temperature（T_C=450℃）near its morphotropic phase boundary（MPB）,which is expected to be used in high temperature multilayer actuators and received widespread attentions of researchers.In this thesis,three major works have been done on the basis of BS-PT piezoelectric ceramics:（1）CaTiO₃（CTO）was introduced into BS-PT piezoelectric ceramics as a third-end member,which can further improve the electrical properties of BS-PT ceramics;（2）CuO was chosen as sintering aid to reduce the sintering temperature of BS-PT ceramics;（3）BS-PT ceramics with low sintering temperature and Ag electrode layers were co-fired to form a multilayer piezoceramic actuator,which can be used in high-temperature environment.The details are listed as following:（1）The（1-x）（0.364BS-0.636PT）-x CTO（x=0-0.03）piezoelectric ceramics were prepared by solid state reaction method.The introduction of CTO could improve the ferroelectric and piezoelectric properties of BS-PT ceramics.Optimal electrical properties were achieved when x=0.01 with piezoelectric constant d₃₃ of 475 p C/N,remanent polarization P_r of 42?C/cm²and Curie temperature T_C of 429?C.Within the temperature range from room temperature to350℃,the piezoelectric performances kept stable.As a result,（1-x）（0.364BS-0.636PT）-x CTO ceramics are one of the promising candidates which are used in high temperature sensors and actuators.（2）The addition of CuO could effectively reduced the sintering temperature of BS-PT piezoelectric ceramics.Among the 0.367BS-0.633PT-x CuO（x=0.1-0.5wt%）piezoelectric ceramics,the sintering temperature was only 930?C for 0.367BS-0.633PT-0.3wt%CuO ceramic and this ceramic possessed the optimal electrical properties with piezoelectric constant d₃₃ of 362 p C/N,remanent polarization P_r of 21.1μC/cm²,electrical-induced strain of 0.26%and Curie temperature T_C of 454?C.Furthermore,the piezoelectric constant d₃₃ at 200℃was333 p C/N.Therefore,0.367BS-0.633PT-x CuO ceramics are suitable to be co-fired with Ag electrode to prepare high temperature multilayer piezoelectric ceramic actuators.（3）0.367BS-0.633PT-0.3wt%CuO ceramic layers and Ag electrode layers were co-fired at 930?C to prepare a multilayer piezoelectric ceramic actuator.The number of actuator layers was 95 with length of 5 mm,width of 4.3 mm and height of 4.3 mm.The thickness of the single ceramic layer was about 44.4μm.The electrical-induced strain of the actuator at room temperature and 200°C under the driving voltage of 200 V were 0.13%and 0.16%,respectively,which is expected to be applied among the high temperature serving devices.On the basis of BS-PT ceramic,the electrical properties were improved by introducing a third-end member and the sintering temperature was successfully reduced by adding CuO.Finally,a driving device was prepared that could be used in high temperature.The performance modifications of BS-PT ceramics are of significance for impetus of research in the related areas.