Preparation And Properties Of Lead Based Piezoelectric Ceramics With High Piezoelectricity And Low Loss

Lead based piezoelectric ceramics are widely used in high-power piezoelectric devices such as ultrasonic transducers,emission hydroacoustic transducers and piezoelectric transformers because of their excellent mechanical and electrical properties and thermal stability.In order to meet the performance requirements of the devices,it is very important to regulate and optimize the mechanical quality factor of the high-power piezoelectric ceramics,reduce the loss and improve the comprehensive performance of the electromechanical devices.In order to solve the problem of the mutual restriction between the piezoelectric coefficient d₃₃and the mechanical quality factor Q_m in the field of piezoelectric ceramics,the lead based piezoelectric ceramics with high piezoelectric properties and low loss were prepared by doping modification,composition,structure and performance were systematically studied.Specific work is as follows:（1）PSZTN-based piezoelectric ceramics doped with Mn CO₃ and Sb₂O₃ were prepared.Based on the chemical reaction of defects,the effects of different dopants on the phase structure,micro-morphology and electrical properties of the ceramics were studied,and the modification mechanism was further explored.It was found that Mn CO₃ mainly acts as a hard dopant,which could effectively improve the mechanical quality factor Q_m of ceramic matrix and weaken the mutual restriction relationship between Q_m and d₃₃.On this basis,the complex doping of Sb₂O₃and Mn CO₃ was carried out,and it was found that Sb³⁺and Sb⁵⁺could occupy the A and B ions in the lattice,and produced lead ion and oxygen ion vacancy,thus acting as both donor dopant and acceptor dopant.Therefore,PSZTN-based piezoelectric ceramics with high piezoelectric properties d₃₃～554 p C/N and low loss Q_m～540 were obtained when the doping amount of Sb₂O₃ was 0.1wt%.The high piezoelectric response was mainly due to the coexistence of two-phase coexistence structure and the contribution of high irreversible domain wall motion.In addition,by optimizing the sintering system of PSZTN-based piezoelectric ceramics doped by Sb₂O₃ and Mn CO₃,it was found that the ceramics sintering at 1250 ^oC for 2 h had dense microstructure and good grain development,which could effectively reduce the mutual restriction relationship between d₃₃ and Q_m.At this time,the d₃₃,k_p and Q_m of the ceramics were566 p C/N,0.657 and 625 respectively.The ceramics also had good temperature stability,the strain value change rate was about 25%in the temperature range of 20 ^oC～200 ^oC,and the depolarization temperature was about 350 ^oC.（2）A ternary system of PMn S-PZT based piezoelectric ceramics doped with Bi(Ni_1/2Ti_1/2)O₃ relaxor ferroelectrics was prepared,and the effects of BNT doping on the structure and properties of PMn S-PZT based ceramics were studied.It was found that Bi³⁺and Ni³⁺replace the A-site and B-site ions of perovskite structure,respectively,and played the role of soft doping and hard doping,so that the dielectric constantε_r～1612 and dielectric loss tanδ～0.0036 were improved together.In addition,the introduction of BNT destroyed the long-range ordered ferroelectric structure of the ceramics and produced local heterogeneous structures.Therefore,when the doping amount of BNT was 0.04,the piezoelectric properties of the ceramics were significantly improved,with d₃₃=366 p C/N,k_p=0.625,Q_m=1557.（3）The effect of Pb(Mn_1/3Sb_2/3)O₃（PMn S）content on the phase structure,microstructure,mechanical and electrical properties and thermal stability of BNT-PMn S-PZT piezoelectric ceramics was systematically studied by changing the phase boundary position of Pb(Mn_1/3Sb_2/3)O₃.It was found that PMn S could induce the phase structure transition from terilateral phase to tripartite phase.When the PMn S content was 0.07,the phase structure of the ceramic was located in the morphotropic phase boundary region,which had high piezoelectric properties,that was d₃₃=384 p C/N,k_p=0.633,Q_m=1388.The ceramic component also had excellent temperature stability,in the temperature range of 20～200 ^oC,the strain change rate was only 8.8%,which was an excellent high-power piezoelectric ceramic material.