The Research On The Properties Of Bi(Mg_0.5Ti_0.5)O₃-PbTiO₃ High Curie Temperature Piezoelectric Ceramics

With the transducer of piezoelectric ceramics widely applied to the high-temperature field such as aerospace and geological exploration et al.It is demanded that the piezoelectric ceramics should obtain the higher and higher Curie temperature,as well as that the dielectric and piezoelectric properties of the ceramics cannot deteriorate too seriously.Thus,it is urgent that the more attention is paid to researching the piezoelectric ceramics owing both high Curie temperature and outstanding dielectric/piezoelectric properties.Curie temperature is namely the critical temperature where the structure of the piezoelectric ceramics transfers between ferroelectric phase and paraelectric phase,and it reflects the ceramic ability of anti-temperature aging.Generally,the higher Curie temperature is,the lager the coercive field is,the more remarkable pinning effect is,the weaker the dielectric and piezoelectric activity is.In principle,the piezoelectric ceramics can only operate normally below the half of Curie temperature,because of the depoling effect.Thus,the high-temperature piezoelectric ceramics should obtain Curie temperature above 400°C,as well as high dielectric and piezoelectric activity.In this paper,emphasis is focused on the Bi(Mg_0.5Ti_0.5)O₃-PbTiO₃ binary piezoelectric ceramic as the substrate material by the traditional solid state method.Curie temperature,as well as dielectric/piezoelectric properties,is modified with the method of substitution and solid solubility.Firstly,it is carried out that the experiment is to get the optimum preparation process of Bi(Mg_0.5Ti_0.5)O₃-PbTiO₃ binary piezoelectric ceramic:PbO,?MgCO₃?₄·Mg?OH?₂·5H₂O et al should be used,in the terms of raw material selection;we can mix and ball mill all the raw materials,then calcine to get the calcined powder in the one-step process,instead of preparing the precursor MgTiO₃ in advance;To?1-x?Bi(Mg_0.5Ti_0.5)O₃-xPbTiO₃ binary piezoelectric ceramic system,x=0.38 can be considered as the morphotropic phase boundary,and the property coefficients of the morphotropic phase boundary are as below:d₃₃=205pC/N?K_p=0.33?Q_m=22?tan?=52*10^-3??_r=1128?T_c=440°C,respectively..When the relax ferroelectric PZN is solid soluted to the substrate material,the dielectric property is improved,while the piezoelectric property and Curie temperature are deteriorated.The comprehensive properties are relatively considerable located where the value of PZN introduction is 1mol%,as following:d₃₃=184pC/N,K_p=0.32,Q_m=18,?_r=1033,tan?=60*10^-3,T_c=420°C,respectively.And the comprehensive optimum sintering process should be that the sinstered temperature is 1050°C,and the holding time is 5 h.In the other hand,when the substitution of BaTiO₃ is introduced,the tetragonality c/a firstly ascends,and then descends.In comparison with the non-substituted ceramic,Curie temperature of all the piezoelectric ceramics with BaTiO₃ substituted increases in some degree.But the dielectric/piezoelectric properties degrade.When the value of substitution is 10mol%,the comprehensive properties is remarkable,as below:d₃₃=180pC/N?K_p=0.32?Q_m=24?tan?=73*10^-3??_r=850?T_c=464°C,respectively.