Study On Modification Of High Temperature Piezoelectric Calcium Bismuth Titanate And High Dielectric Titanium Oxide Materials

Dielectric materials and piezoelectric materials are two kinds of important function of electronic materials.High dielectric material in device miniaturization and high energy density storage of huge applications has always been the hot spot of the study,they have a high dielectric constant(?r>104),low dielectric loss(tan?<5%)and good excellent properties such as high frequency stability.Recent study found that doping TiO2(In,Nb)for the dielectric loss(tan8)In long frequency range is lower than 3%,of its excellent dielectric properties,make its have great potential for development.Therefore,in-depth study of new type(In,Nb)doped high dielectric TiO2 materials will be a promising job.Bismuth layer material is important piezoelectric material,is made up of bismuth layer structure of compound layer andthe grid work of the perovskite structure with overlapping.They are mainly used in high temperature environment,for example,the working temperature of 200?400?in the automobile and aerospace industry,even need to use at higher temperatures,such as nuclear reactors.CaBi4Ti4O15 bismuth layer piezoelectric ceramics with high Curie temperature(Tc=790?)and low dielectric loss(tan?<0.3%),has a great application in high temperature sensor,and scientists from all over the world research hot spot in recent years,the continued doping modification research also has important research significance.Under the background of the study,this thesis mainly studies the(In,Nb)doped TiO2 high dielectric ceramic and AB doped CaBi4Tia4O15 high temperature performance of the piezoelectric ceramic,structure,etc.,the conclusion is as follows:1.(In,Nb)was studied with content of 1%,5%,10%respectively affect the performance of TiO2 ceramic,it is concluded that(In,Nb)doped amount to 5%of TiO2 ceramics with high dielectric constant(?r>104)and low loss(tan??5%),so we chose the TiO2 ceramics for further modification research.Considering In2O3 during sintering process(850??930?)has a high vapor pressure and easy sublimation,so In the original 5%(In,Nb)doping amount on the basis of the increase In the content to make up for In volatilization loss,its formula is:(Nb0.5In0.5)0.05Ti0.95O2+xIn2O3(x=0.00,0.02,0.04,0.06,0.08).Study sample of x=0.04 more dense,density is the largest.In frequency is equal to 7KHz,samples of x=0.04 dielectric loss tan delta with a minimum 1.28%.In 40Hz?100KHz frequency range,the samples of x=0.04 dielectric loss are less than 5%;In 147Hz?100KHz range,the dielectric loss is less than 3%.Sample x=0.04 the relative dielectric constant in 40Hz?1MHz range were greater than 104,the relative dielectric constant with the increase of frequency decline is not obvious,reflects the very good frequency stability.Within the scope of temperature-50??150?,4%more In2O3 samples with minimal dielectric loss;When temperature is 125?,the dielectric loss can still be less than 5%,that the dielectric properties of the components of samples with good temperature stability.2.Study the B bits(W,Nb)composite doping of CaBi4Ti4O15(CBT)ceramics.The structural formula of compound doped for:CaBi4Ti4-x(W,Nb)x/2O15(x=0.00,0.02,0.04,0.06,0.08),B bits(W,Nb)composite doping has greatly increased the CBT piezoelectric constant d33,resistivity and dielectric properties.When x=0.04,the piezoelectric constant d33 for 20 pC/N,far higher than that of pure CBT piezoelectric constant.500?,the resistivity of the sample x=0.04 is still as high as 106? · cm,has good high temperature stability.At room temperature,the thickness of the x=0.04 kt vibration electromechanical coupling coefficients was 21.1%,broad flat vibration electromechanical coupling coefficient kp(5.9%),the dielectric loss is only 0.18%,Qm for 6390 mechanical quality factor,the above data show that high temperature(W,Nb)doped CBT bismuth layer structure of ceramics has been improved obviously.3.AB bits at the same time of CaBi4Ti4O15 doped ceramics was studied the influence of various performance,structural formula is:Ca0.8(Li,Ce)0.1Bi4Ti4-x(W,Nb)x/2O15(x=0.02,x=0.04,x=0.06,x=0.08).AB and doping make material of piezoelectric and dielectric properties are improved a certain extent.Samples of x=0.04 piezoelectric constant d33 from 7 pC/N to 16 pC/N,dielectric loss tan delta is only 0.26%,the thickness of vibration electromechanical coupling factor kt is 17.9%,plane vibration coupling coefficient kp is 4.8%.By AB compound doping,the performance of the modified than pure CBT ceramics Ca0.8(Li,Ce)0.1Bi4Ti3.96(W,Nb)0.02O15 high bismuth layer ceramic.