Preparation And Doping Modification Research Of PLZT Ceramics

PLZT ceramics have excellent ferroelectric,piezoelectric and dielectric properties。It has been widely used in micro-memory,pyroelectric infrared detectors,ferroelectric field effect tubes,micro-machines,flat panel displays and other fields.Ferroelectric materials employed in optical and electro-optical devices must be made sufficiently transparent in the visible region.An important property of PLZT ceramics is the photo-induced strain effect.This effect is generated by absorption of ultraviolet light,and the density of the material can affect its performance.Therefore,it is of great significance to optimize the preparation process and improve the optical and electrical properties.In this paper,PbLa_0.04(Zr_0.52Ti_0.48)O₃ was selected as the research object.It is expected that transparent PLZT ceramics with high density can be prepared by atmosphere sintering.First of all,the preparation process of ceramics was studied.The traditional solid-phase method and sol-gel method were adopted for the preparation of powders.The ordinary ball milling and high-energy ball milling were used to grind powders.Through the analysis of the powder phase,particle size and the density of ceramics,the best method of powder preparation was determined.After that,the effects of PVA,sintering temperature and holding time on the density and properties of PLZT ceramics were studied.Through the analysis of phase,surface morphology and properties,the optimum preparation process was determined:The PLZT powder is prepared using a combination of sol-gel method and high energy ball milling,then it was preheated at 700℃ for 2h,after that 5%PVA was added.At last,the powder was pressed into a ceramic piece and kept at 1250℃ for 2h to obtain a PLZT ceramic.The density of the PLZT ceramic was 99.45%,its overall performance was:ε_r=758.26,tanδ=0.076,d₃₃=192.7 pC/N,P_r=22.60μC/cm².In order to improve the performance of PLZT,ion doping method was used in this study.Dy³⁺,Nd⁵⁺,and Pr³⁺rare earth ions were selected to replace lead ions,W⁶⁺ions replace titanium ions,doping introduces cation vacancies.The influence of different ion doping on the electrical properties of PLZT ceramics was studied,the research results show that doping rare earth ions can effectively improve the electrical properites of the ceramics.The piezoelectric properties of the PLDZT ceramics decrease slightly with Dy³⁺doped,the ferroelectric properties increase first and then decrease,and the dielectric properties become better.When the doping amount of Dy³⁺is 3mol.%,the ceramic density is 7.78g/cm3,and the electrical properties are the best:d₃₃=158.9pC/N,P_r=67.25μC/cm²,ε_r=878.38,tanδ=0.035.The influence of Nd³⁺doped on PLZT ceramics（PLNZT）is similar to that of Dy³⁺doping.When the doping amount of Nd³⁺is3 mol.%,its electrical properties are the best:d₃₃=158.9 pC/N,P_r=67.25μC/cm²,ε_r=758.26,tanδ=0.076.Pr³⁺doped PLZT ceramics（PLPZT）can improve its electrical properties.When the doping amount is 1mol.%,the ferroelectric and piezoelectric properties are optimal:d₃₃=291.4 pC/N,P_r=52.41μC/cm²,and the dielectric properties are best when the doping amount is 4 mol.%:ε_r=941.25,tanδ=0.054.The piezoelectric properties of W⁶⁺doped ceramics（PLZTW）decrease,dielectric and ferroelectric properties increase,and the best electrical properties are got when the doping amount is2 mol.%:d₃₃=344.9 pC/N,P_r=39.53μC/cm²,ε_r=1150.36,tanδ=0.044.In this study,transmittances（T）in the visible wavelength range of 390-780 nm and absorptance（abs）in the UV wavelength range of 250 nm to 390 nm for the PLZT-ceramics which are got by ball milling and sol-gel method and PLZT ceramics doped with Dy³⁺,Pr³⁺,Nd³⁺,and W⁶⁺are detected and analyzed.The results show that the smaller the thickness of the ceramic is,tthe larger the visible light transmittance is.The PLZT ceramic prepared by sol-gel method has the bigger transmittance:T=36.5-44.5%and abs=29.4%.Dy³⁺doping can increase the visible light transmittance and ultraviolet light absorption of the ceramics.When the doping amount is 4 mol.%,the optical properties are best:T=47.3-56.8%,abs=34.6%.The visible light transmittance and ultraviolet light absorption of PLNZT ceramics have been improved,When the doping amount is 3mol.%,the visible light transmittance is the maximum,T=56.4-65.3%,and when the doping amount is 2mol.%,the UV absorption is maximum,abs=34.6%.The visible light transmittance of PLPZT ceramics is smaller than that of PLZT ceramics,and there is a slight increase in UV absorption,when the doping amount is 3mol.%,the maximum abs is 31.5%.W⁶⁺doping can increase the visible light transmittance and ultraviolet light absorption of ceramics.When the doping amount is 3mol.%,the visible light transmittance is the maximum:T=38.4-47.2%.When the doping amount is1 mol.%,the ultraviolet absorption rate is Maximum:abs=38.7%.