Influence Of Microstructure On Light Transmittance And Electrical Properties Of Potassium Sodium Niobate-based Ceramics

Transparent ferroelectric ceramics is a type of multi-functional ceramics which can couple optical,electrical and mechanical properties,showing bright application prospects in the fields of lighting,display and medical imaging.Over the years,lead-based transparent ferroelectric ceramics have been widely concerned by scholars due to their high transmittance and superior electrical performance,however,lead-based materials have caused great harm to human body and the environment,so it is a significant research topic to design new environment-friendly transparent ferroelectric ceramics.As one of the most promising materials to replace lead based transparent ferroelectric ceramics,(K0.5Na0.5)NbO3(KNN)based transparent ceramics have certain transmittance and electrical properties.Recent years,scholars have been improving the transmittance and electrical properties through composition design and process optimization,but the relationship between microstructure,transmittance and electrical properties is still unclear.It is expected to prepare KNN-based transparent ceramics with high transmittance and excellent electrical properties by regulating the microstructure of ceramics from the perspective of composition design.In order to study the effects of microstructure on the transmittance and electrical properties,0.95(K0.5Na0.5)NbO3-0.05Ba(Zn1/3Nb2/3)O3(0.95KNN-0.05BZN)was used as basic system,Li2CO3 and Bi2O3 are selected for dopants to produce large pores,large grains and few pores.The main achievements of this paper are as follows:1.Li2CO3 was selected to produce large pores and large grains.0.95(K0.5Na0.5)NbO3-0.05Ba(Zn1/3Nb2/3)O3-x Li2CO3(0.95KNN-0.05BZN-x Li2CO3,x=0,0.01,0.05,0.10,0.15)ceramics are prepared by traditional solid-state method.The effects of microstructure,sintering technology and phase structure on the transmittance of ceramics are systematically investigated,the results show that the introduction of trace Li2CO3 reduces the pores and improves the transmittance;while as LiBiO2 continues to increase,pores increases and transmittance begins to decrease;when x=0.01,the transmittance in the 780 nm is 30%.2.LiBiO2 was selected as dopant formed by Li2CO3 and Bi2O3 to reduce the pores of the 0.95(K0.5Na0.5)NbO3-0.05Ba(Zn1/3Nb2/3)O3-x LiBiO2(0.95KNN-0.05BZN-x LiBiO2,x=0,0.005,0.010,0.050,0.100)ceramics.The effects of microstructure,such as pores and grain size on the transmittance of ceramics are systematically studied,the results show with the increase of the LiBiO2,the quantity and size of pores are significantly reduced and the transmittance is improved;while as LiBiO2 continues to increase,pores increases and transmittance begins to decrease;when x=0.010,the ceramic has the highest light transmittance(T=65%,780 nm)and a higher dielectric constant(?m=1800).3.Preparing 0.95(K0.5Na0.5)NbO3-0.05Ba(Zn1/3Nb2/3)O3-x Bi2O3(0.95KNN-0.05BZN-x Bi2O3,x=0,0.005,0.010,0.050,0.100)ceramics with few pores by Bi2O3 doping.The phase structure,micro-structure,optical and electrical properties of the ceramics are studied.The results show that with the increase of Bi2O3,the porosity of the ceramics decreases gradually,and the grain size increases dramatically;when x=0.010,the ceramic has the highest light transmittance(T=70%,780 nm)and the maximum dielectric constant(?m=2680).The result offers an effective combination of high transmittance and excellent electrical properties,and provides an excellent candidate material for lead-free transparent ferroelectric ceramics.