Colour And Package Properties Of CaAlSiN₃ Red Phosphor System

As a new generation of lighting,WLEDs have great prospect due to its advantages of high efficacy,environmental protection.Color rendering and luminous efficacy,play a great role in the evaluation system of WLED.At present,the commercial way to produce WLEDs are combining a blue chip with yellow phosphor material as YAG:Ce³⁺.The luminous efficacy of the WLEDs could reach the ideal value,but the color rendering is poor,which could be ascribed to the fast that the lacks of red component in the emission spectrum.As a result of it,the development of WLEDs are limited in the application of high-quality shopwindow lighting.What’s more,matrix structure of red phosphor and package process of WLEDs are two main methods improving the fluorescence properties.To find a red phosphor with high color rendering and luminous efficacy becomes a hot spot.And it is hard to improve the efficacy of LED chip.So the research is needed to obtain evidence for the properties improvement of WLED packaging.On the one hand,CaAlSiN₃:Eu²⁺has a broad emission band,with a result in application of all kind of WLED packaging.In this paper,the fluorescence properties ofCaAlSiN₃:Eu²⁺red phosphor is discussed.The effect by different dope-ion and different solubility of LiSi₂N₃ for the CaAlSiN₃:Eu²⁺red phosphor are also studied.In addition,we also briefly studied the influence of the various combination of phosphor in the WLED packaging.The contents and results were as follows:1.Ca_0.992AlSiN₃:0.008Eu²⁺phosphor was prepared by high temperature solid reaction in a gas pressure sintering furnace.It is necessary to study the phase compositions,light-emitting,electronic properties and the WLED packaging method of the red phosphor.The experimental result indicated that the phosphor powders of Ca_0.992AlSiN₃:0.008Eu²⁺prepared by solid reaction was pure.The phosphor showed a broad band with an emission peak at 650nm under 450nm excitation.And Ca_0.9375AlSiN₃:0.0625Eu²⁺phosphor possessed a indirect wide band gap of3.14eV.The WLED prepared by combining Ca_0.992AlSiN₃:0.008Eu²⁺red phosphor and Sialon green phosphor with a blue LED chip,showing a high Ra of 92.1 and a LER of 101lm/W.2.（Sr,Ca）AlSiN₃:Eu²⁺phosphor was made by doping Sr ion in CaAlSiN₃:Eu²⁺phosphor,which could achieve the adjustment of the emission peak.As showed in the experimental result,the emission peak of（Sr,Ca）AlSiN₃:Eu²⁺phosphor blue shifted form 650nm to 630nm and the intensity of emission decreased.The experimental phenomena could be the result of crystal field splitting in the Eu-5d and the lattice expansion.And Sr_0.8125Ca_0.125AlSiN₃:0.0625Eu²⁺phosphor possessed a indirect wide band gap of 3.24eV.3.In order to balance the color rendering and luminous efficacy of WLED,a narrow-band K₂SiF₆ was used by combining with（Sr,Ca）AlSiN₃ and Lu₃Al₅O₁₂2 in the WLED package.The WLED had a high luminous efficacy（115lm/W）and high colour rendering（Ra=96.9,R9=95.8）with the K₂SiF₆:（Sr,Ca）AlSiN₃:Lu₃Al₅O₁₂2 ratio of 6:0.72:1.4.With the isostructural LiSi₂N₃ increasing,the phosphor showed the blue-shift and spectra broadening ofemissionspectra,along with the enhancement of thermal quench,which was due to the changes of Eu-5d electronic state.The properties was best when the addition of LiSi₂N₃ was 0.2mol.The effect of different phosphor combinations in the WLED packaging was determined.The WLED prepared by combining Ca_0.79Li_0.2Al_0.8Si_1.2N₃:0.01Eu²⁺and Lu₃Al₅O₁₂:Ce³⁺,had a high LER of101lm/W and a high Ra=95,R9=96.