| Bismuth layered piezoelectric materials are the most promising materials in high-temperature piezoelectric devices fields.However,due to the ferroelectric polarization rotation orientation is restricted to the two-dimensional space and large coercive field,resulting in them low piezoelectric constant,which greatly limits its practical application in high-temperature piezoelectric fields.For phase composition of calcined powder dependence of electrical properties of the bismuth layered piezoelectric ceramics.The internal relationship of modified ion characteristics(radius,electronic structure and concentration),variable valence ion doping and second phase strengthening of grain boundary with system lattice distortion,electrical conductivity,piezoelectric properties and temperature stability.In this paper,the phase composition of the calcined powder is adjusted by optimizing the calcination process,analyzed its influence on the electrical properties of ceramics;A-site modification of the bismuth layered piezoelectric material is performed by the combination of alkali metals and rare earth ions with different ion radii,valence states and concentrations,the intrinsic relationship between the characteristics of the modified ions and the ceramic cell parameters,electrical conductivity and piezoelectric properties are studied.The ceramic grain boundary can be strengthened by add to oxide(ZnO),explored the preparation process of composite ceramics,the effects of oxide content and preparation process parameters on the electrical resistance and piezoelectric properties of composite ceramics are studied.BaBi4Ti4O15 ceramic were synthesized by using the solid-state reaction method with different calcining temperatures.It can be found that the orientation of the crystal structure,piezoelectric coefficient,and remnant polarization were dependent significantly on the calcining temperature of the BBT ceramics.The concentration of oxygen vacancies can be effectively reduced with the decrease in the calcining temperature,the significantly improved in the electrical performance of the BBT ceramics could be attributed to the inhibition in the domain wall pinned by oxygen vacancies with the decrease in the calcining temperature.The maximum of piezoelectric coefficient was 23 pC/N for the ceramic with the calcining temperature of 780℃,together with Cutie temperature of 422℃ and remnant polarization of Pr=4.9 μC/cm2.A-site LiX(X=La,Ce,Gd,Lu)double-ion modified SrBi2Nb2O9(SBN)ceramics were prepared by solid-state reaction.It can be found that Sr0.5(LiLa)0.25Bi2Nb2O9 ceramics obtained high piezoelectric and ferroelectric properties,and its piezoelectric constant and residual polarization strength reach up to 26 pC/N and 7.09 μC/cm2,respectively;With the change of LiLa content,Sr0.7(LiLa)0.15Bi2Nb2O9 ceramics obtained the maximum piezoelectric constant(29 pC/N),high Curie temperature(475℃)and good temperature stability of piezoelectric properties.It can be found that with the increase of LiCe content,the conductivity is improved significantly,Sr1-x(LiCe)x/2.5Bi2Nb2O9(SBN-xLiCe,x=0,0.1,0.3,0.5)ceramics exhibited the transition from normal ferroelectrics to relaxor ferroelectrics.Oxygen vacancy is confirmed to be responsible for the conductivity at high temperature by calculating activation energy of the carriers in the corresponding range of high temperature.Dielectric relaxation behavior at high temperature is attributed to the short-range conductivity of oxygen vacancies.SrBi2Nb2O9-xZnO(SBN-ZnO)composite piezoelectric ceramics prepared by Solid State Process.It can be found that the preparation process of composite piezoelectric ceramics and the addition of zinc oxide have a significant effect on the piezoelectric properties.Firstly,SBN ceramics were activated sintered,during the sintering process,rapid heating,cooling and shortening the holding time were needed.When the sintering temperature was 980℃,the piezoelectric constant of SBN-0.1ZnO ceramic was 20 pC/N,which was 25%higher than that of SBN ceramic. |
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