Study On The Synthesis,Structure And Properties Of Carbonitride Phosphor For Full-spectra Lighting

With the increasing pursuit of healthy high-quality life,the w-LED for full-spectra lighting(FSL)have been developed and popularized in the lighting field.As the core materials of w-LED,phosphors are the key to realize full spectrum lighting with continuous and uniform spectra.In terms of spectrum,the carbonitride phosphors RE2Si4N6C:Ce3+(RE=Y,Gd,Lu)match perfectly with the purple/near-ultraviolet LED chips used for full-spectra lighting.Our present work centres on the reaction mechanism,modification of luminescent properties via unit co-substitution and ionic solid solution,and exploration for new matrix.Firstly,the reaction mechanism of traditional carbothermal reduction nitrification method for preparing RE2Si4N6C:Ce3+ has been studied and existing problems were pointed out.To optimize the performance,we proposed to synthesize RE2Si4N6C:Ce3+ by high-temperature solid-state reaction method using REH3 instead of RE/REN as raw materials.The behaviors of REH3 and SiC were investigated,as well as the reaction mechanism,which provide theoretical guidance for optimizing the synthesis process.The pure RE2Si4N6C:Ce3+phosphors with better crystallization were synthesized by high-temperature solid-state reaction method and the structure,luminescent properties were investigated.Secondly,the effect of the substitution of Al-N for Si-C on the skeleton structure in Y2Si4N6C:Ce3+ was studied.By means of X-ray powder diffraction and NMR,it was confirmed that A1 successfully entered the matrix lattice in the form of[AIN4]tetrahedron,and its solid solubility was about 60 mol%.It showed that the local structure surrounding Ce3+ would be compressed after replacing Si-C with Al-N,and the Ce-N became shorter,which resulting a redshift on the emission spectrum.In addition,the replacement of Al-N will expand the band gap of Y2Si4N6C and enhances its thermal quenching performance.Thirdly,series of(Y1-xREx)2Si4N6C:Ce3+(RE=La,Gd,Lu)solid solutions were synthesized.The effects of x value and RE on the structure,luminescence and thermal quenching properties of the samples were studied.It was found that Gd and Lu formed total solid solution,while it caused structural changes when the doping La was more than 0.2.The occupancies of La,Gd and Lu ions in matrix were discussed.The local environments around Ce3+ ions changed with the change of RE and x,which led to the emission color tuning from blue-green to orange-red.Finally,based on the rule of structural evolution between RE2Si4N6C and ARESi4N7,the effect of ionic radius difference on the structure of t carbonitrides was illuminated,and a relationship between the structure and ionic radius difference was established.According on the relationship,series of REScSi4N6C carbonitride in hexagonal system were designed and prepared successfully.The crystal structure was accurately analyzed by means of synchrotron radiation single crystal diffraction,transmission electron microscopy,and elemental analysis.The luminescence properties and related mechanisms of Ce3+ doped YScSi4N6C were studied in detail.Under the excitation of n-UV light,the YScSi4N6C:Ce3+ emitted cyan light peaking at 469 nm,and the half-wave width is 98 nm,which can effectively supplement the "green light gap" in current white LED.