Study On Modification Of Lead-Free Piezoelectric Ceramics Of Bismuth Sodium Titanate

Sodium bismuth titanate(BNT)is a kind of lead-free piezoelectric ceramics,which has great potential value,but its application is limited due to low piezoelectric properties.We hope to improve the electrical properties of BNT by doping ions,and analyze the mechanism of the change of electrical properties.Firstly,BNT ceramics were modified with K+and Nb5+at A/B sites by traditional solid phase method.When doped with 0.22 mol K+,the dielectric constant of the sample is 1844,the piezoelectric constant is 172 pC/N,and the maximum dielectric constant at Curie temperature is 7182.The samples doped K+show excellent temperature stability of dielectric constant at high temperature(180?420?).On this basis,Nb5+was doped continuously,and bismuth titanate(Bi2Ti2O7)in pyrochlore phase was formed.The maximum dielectric constant is increased to 2240,and the temperature stable range of dielectric constant is extended to 100-400?.Then,the(1-x)Bi0.5(Na0.78K0.22)0.5TiO3-xBaTiO3 binary system was prepared by traditional solid-phase method and sol-gel method respectively.Both methods can form morphotropic phase boundary(MPB).The introduction of B aTiO3 can inhibit the growth of grains.The samples prepared by sol-gel method have smaller grain size and larger density.The piezoelectric constant of the sample prepared by solid-state method is further increased to 184 pC/N.Finally,the ternary system(0.94-x)BNKT-0.06BT-xSBT was constructed by introducing strontium bismuth titanate using traditional solid phase method.With the increase of SBT,the tetragonal phase content and crystallinity of the sample increase;the grain size of the sample increases first and then decreases,reaching the maximum value at 0.05SBT component;and Td is close to room temperature at 0.07SBT component;the piezoelectric constant of the sample decreases with the increase of SBT doping amount.Figure 46;Table 7;Reference 62...