Study On Preparation And Properties Of Inorganic Phosphor Materials

At present,solid-state lighting is led by the white light-emitting diodes（WLED）,which is generally composed of a blue InGaN LED chip with a yellow-emitting phosphor(YAG:Ce³⁺)that dispersed and encapsulated by silicone.However,this encapsulation faces serious silicone aging problem and heavy thermal quenching of phosphor in high-power LEDs/LDs.Ceramic phosphor plates（CPPs）have high thermal stability/conductivity,very promising for high-power application.This work focuses on the preparation and study of several inorganic phosphors in the forms of powder and CPP,which includes:1)CPP samples containing YAG:Ce³⁺.YAG:Ce³⁺powder of submicro-size was prepared by co-precipitation method.Then the corresponding CPP samples were prepared by pressing the previous phosphor to a pellet followed by high temperature sintering.After sample preparation,the influences of Ce³⁺concentration on the luminescence intensity of YAG:Ce³⁺phosphor in both forms of powder and ceramic were studied.As demonstrated that the optimum concentration of Ce³⁺was 1%.Based on YAG:Ce³⁺phosphor/CPP,the influence of the introduction of Al₂O₃ phase was studied.The result shows that the addition of Al₂O₃ did not increase the photoluminescence（PL）intensity of YAG:Ce³⁺ceramics,which may be due to the insufficient density of the prepared CPPs.2)Green phosphor with formula of BaMgAl₁₀O₁₇:Mn²⁺.Four phosphors with formular of BaMgAl₁₀O₁₇:Mn²⁺,SrMgAl₁₀O₁₇:Mn²⁺,BaZnAl₁₀O₁₇:Mn²⁺,SrZnAl₁₀O₁₇:Mn²⁺were prepared,with the latter three materials newly designed.These materials exhibit strong and narrow green emission.The results show that Sr²⁺substituting for Ba²⁺decreases the luminescence saturation concentration of Mn²⁺,and Zn²⁺substituting for Mg²⁺has no such an effect.Among them,the new green phosphor BaZnAl₁₀O₁₇:Mn²⁺has good thermal stability,and its PL intensity did not decline under 200°C,showing its great potential for high power applications.Furthermore,in order to increase the absorption of Mn²⁺in phosphor BaMgAl₁₀O₁₇:Mn²⁺,Ce³⁺and Li⁺dopants were introduced.It shows that doping Ce³⁺can improve BaMgAl₁₀O₁₇:Mn²⁺absorption,due to the transfer energy from Ce³⁺to Mn²⁺.The optimal doping ratio is BaMgAl₁₀O₁₇:0.04Ce³⁺,0.04Li⁺,0.40Mn²⁺.3)BaZnAl₁₀O₁₇:Mn²⁺CPPs were prepared by a two-step process.Firstly,BaZnAl₁₀O₁₇:0.40Mn²⁺powder was prepared by co-precipitation method with high temperature sintering.At temperature range of 1200-1600°C,a single BaMgAl₁₀O₁₇ phase appears and the impurity phase disappears at 1500°C.This synthesis temperature is nearly 200°C lower than the solid phase method.Using the above-mentioned BaZnAl₁₀O₁₇:0.40 Mn²⁺phosphor prepared at1200-1300^oC as the starting material,a dense BaZnAl₁₀O₁₇:0.40Mn²⁺CPP was successfully prepared at 1700°C.Its emission peak is around 517 nm and can be excited by blue light at 455nm.