Study On The Properties And Doping Modification Of PZN-PZT Ternary Piezoelectric Ceramics

0.3PZN-0.7PZT ternary system piezoelectric ceramics was selected as research object, the effect of Zr/Ti ratio on its morphotropic phase boundary, dielectric and piezoelectric properties was studied. The results showed that the system lies in morphotropic phase boundary when Zr/Ti ratio is between 51/49 and 48/52.The best properties are abtained when Zr/Ti ratio is 49/51.The main parameter values are:ε₃₃ T/ε₀=2580, d₃₃=440pC/N, Kp=65%, tanδ=1.7%,Tc=286℃.This article has also studied the influence of sintering temperature on the microstructure and properties, the result indicated: The best temperature is 1230℃for two hours at which time the crystal grain grows evenly and compactively, the particle size is 3～5 um . In addition, the doping modification of PZN-PZT system piezoelectric ceramics were studied. Combined with SEM pictures, some conclusions can be drawed by analyzing the influence of the oxide dopants such as Ta₂O₅ and Sb₂O₅ upon the material properties, the optimal doping amounts of Ta₂O₅ and Sb₂O₅ are 0.2wt% and 1wt% respectively. The material properties can be improved obviously with 0.2wt% Ta₂O₅ doping compared with Sb₂O₅: d₃₃=450pC/N, Kp=0.66,εT33ε0=2570,Qm=80, tanδ=1.8%.The Sb₂O₅ doping can promote the growth of crystal grain, reduce the sintering temperature in a certain extent. Moreover, this article has approached the research on the influence of Sb2O3 doping forms and the Sb ion valent states on the electrical properties and the temperature stability of the Pb0.95Ba0.05(Zn1/3Nb2/3)0.3(Zr1/2Ti1/2)0.7O3 ceramics. The results indicated that certain doping amout can improve the electrical properties. Compared to the substitutional doping form, the electromechanical properties are better when doped with the additional form, but the resonant frequency stability to the temperature is worse.εT33ε0, d₃₃, Kp and tanδcan get the best values when the Pb0.95Ba0.05(Zn1/3Nb2/3)0.3(Zr1/2Ti1/2)0.7O3 ceramics sintered at 1270℃, doped with two kind of valent states (Sb³⁺and Sb⁵⁺),εT33ε0reached 3217 and 3357 respectively, but the tanδappeared opposite tendency along with the temperature changing. The Sb³⁺ doping had high resonance frequency, below the room temperature, the temperature stability was better when doped with Sb⁵⁺ compared to Sb³⁺, but there was no obvious difference above room temperature. Along with the temperature change, the changing tendency of Kp was gentle,â–³K_p/K_p20℃% had the same changing tendency, from the negative temperature coefficient to the positive temperature coefficient. When doped with Sb⁵⁺, the stability of the ceramics was better.Finally this article has studied the effect of heat treatment, the sintering prosess and buries on the properties, we can obtained the conclusions that the heat treatment, proper sintering prosess and correct choice of buries can enhance the dielectric and the piezoelectric properties effectively.