Preparation And Modification Of PYN-PHT Ternary Piezoelectric Ceramics

Piezoelectric ceramics have the ability to convert between electrical energy and mechanical energy,and have been widely used in the field of piezoelectric devices such as sensors and transformers.Due to the development of science and technology,higher requirements are put forward for devices used in high-temperature fields such as aerospace and automobile industry.Piezoelectric ceramics that have high Curie temperature and can maintain excellent electrical properties in a wide operating temperature range have become research hot spot.In this paper,Pb(Yb,Ni)O₃-Pb(Hf,Ti)O₃(PYN-PHT)ternary piezoelectric ceramics with high Curie temperature and high voltage electrical properties were synthesized by solid phase method,and added to aid sintering modification of reagents and doping ions,and analyze their respective mechanisms of action on the microstructure and electrical properties of the system.The main contents are as follows:The solid phase method is a commonly used method for synthesizing perovskite structure ceramics.The key point of this method is the control of the pre-sintering temperature and sintering temperature in the sintering preparation.It can be inferred that the pre-sintering temperature range of the ceramic system is 800??850?through the powder thermal weight loss-differential thermal analysis,and different component ratios are selected near the quasi-homotype phase boundary of the PYN-PHT ceramics,that is,for x Pb(Yb_0.5Nb_0.5)O₃-(1-x)Pb(Hf_0.4Ti_0.6)O₃(x=0.16?0.22)andx Pb(Yb_0.5Nb_0.5)O₃-(1-x)Pb(Hf_0.45Ti_0.55)O₃(x=0.08?0.12)were prepared separately,and the effects of different pre-sintering temperature and sintering temperature on two Hf,Ti ratio system ceramics were explored,and the best pre-sintering temperature and sintering temperature of the ceramic were obtained.They are 825°C and 1200°C respectively.When Hf:Ti=45:55,x=0.09,that is,0.09PYN-0.91Pb(Hf_0.45Ti_0.55)O₃ is the best component of ceramics,its piezoelectric constant d₃₃,dielectric constant?_r,Curie temperature T_c,electromechanical coupling coefficient k_p,mechanical quality factor Q_m and dielectric loss tan?are 486p C/N,1380,337?,0.46,30 and 1.14%,respectively.The preparation of multilayer piezoelectric transformer parts requires ceramics to have the characteristics of low sintering temperature.At the same time,lowering the sintering temperature can reduce the loss of Pb element and stabilize the atomic ratio of the system.In order to reduce the sintering temperature of ceramics,a V₂O₅ sintering aid was added to0.09PYN-0.91Pb(Hf_0.45Ti_0.55)O₃ ceramics,and the effect of V₂O₅ doping on the microstructure and electrical properties of the ceramics was systematically studied.The study found that the ceramic bulk density and crystal grain uniformity after the addition of V₂O₅ were significantly improved,and after the continued addition of V₂O₅,it was found that the microscopic morphology became worse and the density decreased.When the doping amount of the sintering aid is 0.075wt.%,the sintering temperature of the ceramic is successfully reduced by 150?,and the piezoelectric constant d₃₃ is increased to 490p C/N,and the electromechanical coupling coefficient k_p is 0.59.Piezoelectric devices with high mechanical quality factor can well overcome the energy loss caused by mechanical motion under resonance.The doping modification of PYN-PHT ceramics by WO₃ improves the mechanical quality characteristics of the ceramic system.Studies have found that WO₃ can effectively reduce the pore in the grain boundaries to increase the density of ceramics,promote the formation of a good microstructure,and the dense grain boundaries are conducive to spontaneous polarization direction deflection and improve the mechanical quality factor Q_m.When the doping amount of WO₃ is 0.1wt.%,the mechanical quality factor Q_m of the ceramic can be effectively improved to 38.6,but the dielectric properties of piezoelectric ceramics are significantly reduced,and the piezoelectric performance has not been improved.This is because W⁶⁺ions are easily combined with other substances in the powder.Related to the formation of miscellaneous phases.