Study On Structural Regulation And Coexistence Of Electrical And Optical Functions Of Rare Earth Doped KNN-Sr(M_0.5Ta_0.5)O₃（M=Yb,In） Fluorescent Transparent Ferroelectric Ceramics

K_0.5Na_0.5NbO₃（KNN）based ceramics have excellent ferroelectric,pyroelectric and piezoelectric properties,and are considered as one of the potential substitutes for lead based ceramics.In this paper,using KNN as substrate,Sr(M_0.5Ta_0.5)O₃（M=Yb,In）as the second component,transparent ceramics with certain ferroelectric properties were prepared by adjusting the composition.On this basis,rare earth Er or Ho was added to make the ceramics have up-conversion luminescence properties.The effects of the content of the second component on the structure,optical and electrical properties of ceramics were detailedly studied,and the changes of the structure and properties of ceramics doped with Er or Ho were preliminarily explored.The main research contents are as follows。（1）The（1-x）K_0.5Na_0.5NbO_3-xSr(In_0.5Ta_0.5)O₃（x=0.02,0.03,0.04,0.05,0.06,0.07）ceramics were designed and prepared.The effects of Sr(In_0.5Ta_0.5)O₃ content on the structure,transparency,ferroelectric and dielectric properties of the ceramics was studied.Research shows that the introduction of Sr(In_0.5Ta_0.5)O₃ makes the crystal structure of the ceramics gradually change from orthorhombic phase to pseudo cubic phase.With the increase of Sr(In_0.5Ta_0.5)O₃ content,the grain size of the ceramics increases gradually and the density decreases;when x=0.04,the transmittance of the ceramics reaches the maximum value of 46.9% at the wavelength of 1100 nm.With the increase of Sr(In_0.5Ta_0.5)O₃ content,the electrical properties of the ceramics decrease gradually,the maximum dielectric constant decreases from 4990 to 1660,and the remanent polarization decreases from 11.2μC/cm² to 5.4μC/cm².（2）The（1-x）K_0.5Na_0.5NbO_3-xSr(Yb_0.5Ta_0.5)O₃（x=0.005,0.01,0.02,0.03,0.04,0.05）ceramics were designed and prepared.The effects of Sr(Yb_0.5Ta_0.5)O₃ content on the structure,transparency,ferroelectric,energy storage and dielectric properties of the ceramics was studied.The results indicate that all the ceramics exhibit pure perovskite phase structure,and the phase structure changes to pseudo cubic phase with the increase of Sr(Yb_0.5Ta_0.5)O₃ content at room temperature,and the grains become smaller and the density increases.With the increase of Sr(Yb_0.5Ta_0.5)O₃content,the transmittance of the ceramics first increases and then decreases.When x=0.01,the transmittance of the ceramics reaches the maximum value of 68.2% at1100 nm,and the optical band gap is 3.00eV.At this time,the comprehensive energyy storage performance of the ceramics reaches the best,and the energy storage density and energy storage efficiency are 0.55J/cm³ and 61.1%respectively.When x=0.005,the dielectric constant reaches the maximum value of 3300.（3）Ho doped 0.98KNN-0.02SYb T-x%Ho（x=0.1,0.3,0.5,0.6,0.65,0.7）transparent ceramics were prepared.The effects of Ho content on the structure,transparency,up-conversion luminescence,ferroelectric,energy storage and dielectric properties of the ceramics were studyed.The results indicate that the 0.98KNN-0.02SYbT ceramics with Ho ions all form a single perovskite structure,and the ceramics have a pseudo cubic structure at room temperature,and the doping of Ho ions makes the grains of the ceramics gradually increase and the density decrease.At the same time,with the increase of Ho content,the transmittance of the ceramic decreases gradually.The maximum transmittance of ceramics at x=0.1 is 53.4%（1100nm）.When x=0.6,the luminescent intensity of the ceramic reaches the highest,and the luminescent intensity of the ceramic decreases obviously with the addition of Ho ions.At this time,the comprehensive energy storage performance of the ceramic reaches the best,and its energy storage density and energy storage efficiency are 0.16J/cm³ and 69.4% respectively.（4）Er doped 0.98KNN-0.02SYbT-x%Er（x=0.2,0.3,0.3,0.5,0.6,0.7）transparent ceramics were prepared.The effects of Er content on the structure,transparency,up-conversion luminescence,ferroelectric and dielectric properties of the ceramics were studied.The results indicate that the phase structure of the ceramics is not changed by the introduction of Er ions,and the phase structure is still pseudo-cubic phase.Er doping increases the porosity,increases the grain size and decreases the density of the ceramics.At the same time,with the increase of Er content,the transmittance of the ceramic decreases gradually.When x=0.2,the transmittance of the ceramic reaches the maximum value of 46.3%（1100 nm）,and the band gap of the ceramic is 2.97eV.In addition,Er doping makes the ceramics show better up conversion luminescence properties.When x=0.5,the luminescence intensity of the ceramics reaches the highest.With the increase of Er content,the luminescence intensity decreases.When x=0.1,the dielectric temperature spectrum shows that the dielectric constant reaches the maximum value of 3094.