Fabrication And White LED Research Of High-performance Ce:LuAG Phosphor Ceramics

White light-emitting diode（WLED）,as a new type of light emitting device,has received more and more attention in recent years due to its small size,energy saving,long life,environmental friendliness,and other excellent performance.At present,the main commercial LEDs are composed of blue LED chips and Ce:YAG yellow phosphor,which is coated on the surface of the chips by organic resin or silicon.However,due to the poor thermal conductivity and chemical stability of the resin,it is easy to age and turn yellow after a long time of use,which eventually leads to the decrease of the luminous intensity of WLED and the drift of color temperature.These problems are more obvious under high-power illumination.This kind of lighting scheme cannot meet people’s lighting requirement gradually,so it is imperative to replace the commercial phosphor with new type of phosphor conversion material.Ce:YAG phosphor ceramics can solve the problems caused by phosphors as phosphor conversion materials.Ce:YAG ceramics with high thermal conductivity（approximately 15 W/m K）and good mechanical and optical properties have become a good candidate material to meet the needs of next-generation lighting（high output power）.As a high-power lighting material,good thermal stability is a necessary condition,Ce:LuAG is much better than Ce:YAG,more suitable for high-power lighting.However,the color rendering index of Ce:LuAG ceramics is still lower than that of Ce:YAG.The optical performance of the ceramic must be improved before the color rendering index of Ce:LuAG fluorescent ceramics is improved.In this paper,Ce:LuAG ceramics are studied from the following three aspects:（1）The good optical quality of Ce:LuAG phosphor ceramics is the premise of the improvement of the CIR.Ce:LuAG and LuAG ceramics have the same optical quality improvement scheme.This paper proposes for the first time that the pretreatment of Lu₂O₃ commercial powder can control the sintering activity,specific surface area,and adsorption of impurities.The Ce:LuAG transmittance has been successfully increased from 11.4%to 68.4%without the addition sintering aids.The effects of pretreatment at different temperatures on the optical properties of the powder and the prepared ceramics are revealed.Calcining the Lu₂O₃ powder in a suitable temperature can effectively remove the adsorbate while maintaining the sintering activity of the powder.The LuAG transparent ceramics prepared by pretreatment at 1000°C have no pore in the microstructure and the highest linear transmittance at 1064 nm is 68.4%.（2）Using Ce:LuAG as the phosphor conversion material,the CRI of WLED is obviously lower because of the lack of red light.By adjusting the crystal field intensity of Ce:LuAG,the lack of red light can be compensated effectively.By substituting Mg²⁺/Si⁴⁺pairs for Al³⁺/Al³⁺pairs,the Ce O₈ polyhedron was compressed and the emission spectra shifted from green to yellow bands.This paper specifically studies the changes in the luminescence properties of Ce:LuAG ceramics and the evolution of the ceramic unit cell structure after Mg/Si gradually replaced Al/Al.The spectra of substituted Ce:LuAG phosphor ceramics showed a red shift of 25 nm,the color index increased from 58.4 to 70.4,and the color temperature decreased from 6471 to 4062.Variations in emission wavelengths make it easy to adjust the color characteristics of solid-state devices for different applications.（3）In order to further improve the color index of Ce:LuAG phosphor ceramics and to improve the uniformity of luminance,the missing red-light components were made uo by co-doping Cr³⁺in Ce:LuAG ceramics and energy transfer between Ce and Cr.The color index of Cr,Ce:LuAG ceramics prepared by co-doping is increased from51.8 to 74.7.In addition,In addition,through the superposition design of Cr,Ce:LuAG and Ce:YAG,the small refractive index difference between LuAG and YAG is used to improve the blue light utilization rate,solve the blue spot problem caused by the high transmittance of LuAG fluorescent ceramics,and realize the synthesis of white light.Even,the color rendering index has been further increased to 88.This paper not only provides different technical solutions for the red light component in the study of high-power solid-state lighting phosphors conversion materials,and promotes the development of the solid-state lighting.At the same time,the adjustable emission band also provides a reference for the research of fluorescent conversion materials for display projection and plant lighting.