Preparation And Research On Optical/Electrical Properties Of Potassium Sodium Niobate-Based Energy Storage Ceramics

Dielectric energy storage ceramics are widely used in pulse equipment because of their high power rate instantaneous discharge characteristics.With the development of science and technology,people’s demand for multifunctional devices is increasing,and the research and exploration of multifunctional dielectric energy storage ceramics are also increasing.Potassium sodium niobate(K_0.5Na_0.5NbO₃,KNN)based ceramics are not only excellent dielectric energy storage ceramic materials,but also exhibit excellent transmittance after doped with secondary phase of ABO₃ type.They are also excellent candidates in the direction of optical functional ceramics.However,the energy storage performance of KNN based ceramics with optical functions is generally not satisfactory.In order to further prepare KNN-based ceramics with optical function under the premise of ensuring the energy storage performance,this paper mainly adopts the method of doping modification,first by doping the KNN matrix with the appropriate secondary component to control the phase boundary,inhibit the grain growth,and introduce the polar nanoregions;Then,the KNN-based energy storage ceramics with excellent electrical and optical properties can be obtained by adding rare earth elements La³⁺and Er³⁺to make the ceramics obtain light resistance and up-conversion luminescence properties.The main contents of this paper are as follows:（1）（1–x）(K_0.5Na_0.5)NbO₃–x Bi(Li_0.5Nb_0.5)O₃transparent ceramics were prepared by solid state method.The results showed that the appropriate amount of secondary phase Bi(Li_0.5Nb_0.5)O₃ can effectively inhibit grain growth,reduce the size of polar nanoregions,improve the maximum polarization,and improve of energy storage performance and light transmittance.The final preparation has an average grain size of about 109 nm,W_rec of 4.39J/cm³,ηof 81.4%,transparency of 77.9%at ceramic samples.（2）0.85(K_0.5Na_0.5)NbO₃–0.15Bi(Zn_0.5Ti_0.5)O₃–x mol%La³⁺energy storage ceramics with different La³⁺doping were prepared by solid state method.The ceramic with 1 mol%La³⁺doping content is further improved by viscous polymer process.The results show that La³⁺doping can increase the band gap,reduce oxygen vacancies,and induce the generation of super-parametric cubic phase.And the viscous polymer process can effectively reduce the grain size and eliminate pores.The reduction of defects is beneficial to improve the energy storage performance and light resistance of ceramics.The final prepared ceramic has W_rec of 8.11 J/cm³,ηof 80.9%with excellent light resistance.（3）0.95(K_0.5Na_0.5)NbO₃–0.05Bi(Li_0.5Nb_0.5)O₃–x mol%Er³⁺ceramics with different amounts of Er³⁺doping were prepared by solid state method.The results showed that the doping of Er³⁺induced the transformation of the ceramics to tetragonal phase and increased the grain size,resulting in the increase of the polarization intensity of the ceramics,but not conducive to its breakdown field strength,energy storage efficiency and transmittance.The up-conversion luminescence intensity of the ceramics is more than twice as high as that of the low-doped Er³⁺when the doping amount reaches 0.8 mol%.The final prepared ceramic has W_rec of 2.77 J/cm³,ηof 73.9%,transparency of 59.5%,and emits green light of～550 nm and red light of～670 nm under 980 nm incident light.