Phosphor and light emitting device

Abstract

The present invention provides a phosphor, including a constituent having the formula Ca p Sr q M m -A a -B b —O t —N n :Z r , in which M selected from the group consisting of magnesium, barium, beryllium and zinc; A selected from the group consisting of aluminum, gallium, indium, scandium, yttrium, lanthanum, gadolinium and lutetium; B selected from the group consisting of silicon, germanium, tin, titanium, zirconium and hafnium; Z selected from the group consisting of europium and cerium; 0<p<1; 0≦q<1; 0≦m<1; 0≦t≦0.3; 0.00001≦r≦0.1; a=1, 0.8≦b≦1.2; and 2.7≦n≦3.1. Moreover, the normalized dissolved content of calcium of the phosphor is 1˜25 ppm, thereby obtaining a phosphor of high brilliance in the 600˜680 nm region. In addition, the present invention at the same time provides a high brilliance light emitting device.

What is claimed is: 
     
         1 . A method of preparing a phosphor, comprising:
 preparing a calcium raw material, comprising firing calcium metal in an atmosphere of nitrogen gas at a heating rate of 3-5° C./min when a firing temperature is lower 150° C. than the melting point of calcium metal, at a firing temperature of 600-900° C., and at a nitrogen flow rate of 10˜70 liters/min;   performing a mixing step, comprising mixing the calcium raw material with a strontium raw material, oxide and/or nitride of element A, oxide and/or nitride of element B, oxide, nitride and/or metal of element Z, and/or oxide of element M according to a specified weighing proportion for forming a mixture and placing the mixture into a crucible, wherein A is selected from the group consisting of aluminum, gallium, indium, scandium, yttrium, lanthanum, gadolinium and lutetium, B is selected from the group consisting of silicon, germanium, tin, titanium, zirconium and hafnium, Z is selected from the group consisting of europium and cerium, and M is selected from the group consisting of magnesium, barium, beryllium and zinc; and   performing a phosphor firing step on the mixture at a temperature of above 1200° C. and below 2200° C. with a heating rate of 3-15° C./min.   
     
     
         2 . The method of preparing the phosphor according to  claim 1 , wherein the phosphor comprises a constituent having formula—Ca p Sr q M m -A a -B b —O t —N n :Z r ; 0<p<1; 0≦q<1; 0≦m<1; 0≦t≦3; 0.00001≦r≦0.1; a=1, 0.8≦b≦1.2; and 2.7≦n≦3.1; and a normalized dissolved content of calcium of the phosphor is 1˜25 ppm; wherein the normalized dissolved content of calcium is determined by the following method: a phosphor with electrical conductivity lower than 200 μs/cm is prepared and pure water was added according to a 1:100 proportion by weight of the phosphor to pure water, thereby forming a mixed solution of the phosphor and water, after heating for 40 hours at a temperature of 80° C., the mixed solution is then cooled to room temperature, and the aqueous phase of the mixed solution is taken to determine the normalized dissolved content of calcium. 
     
     
         3 . The method of preparing the phosphor according to  claim 2 , wherein the normalized dissolved content of calcium is 5˜20 ppm. 
     
     
         4 . The method of preparing the phosphor according to  claim 2 , wherein a normalized dissolved content of strontium is 3˜17 ppm. 
     
     
         5 . The method of preparing the phosphor according to  claim 1 , wherein the calcium raw material is calcium nitride prepared by firing calcium metal in the atmosphere of nitrogen gas, the firing temperature is 700-800° C., and a firing time for the calcium nitride is 3-12 hours. 
     
     
         6 . The method of preparing the phosphor according to  claim 1 , wherein the calcium raw material is calcium nitride prepared by firing calcium metal in the atmosphere of nitrogen gas, and the nitrogen low rate is 30˜50 liters/min. 
     
     
         7 . The method of preparing the phosphor according to  claim 1 , wherein the calcium raw material is calcium nitride prepared by firing calcium metal in the atmosphere of above 99.99% nitrogen gas. 
     
     
         8 . The method of preparing the phosphor according to  claim 1 , wherein when preparing the calcium raw material, a heating rate from a medium temperature to a retained temperature is lower than a heating rate from room temperature to the medium temperature. 
     
     
         9 . The method of preparing the phosphor according to  claim 8 , wherein the heating rate from the medium temperature to the retained temperature is 3-5° C./min. 
     
     
         10 . The method of preparing the phosphor according to  claim 8 , wherein the medium temperature is 650° C. 
     
     
         11 . The method of preparing the phosphor according to  claim 1 , wherein when preparing the calcium raw material, the method further comprises reducing a heating rate of firing calcium metal when the firing temperature is lower 150° C. than the melting point of calcium metal. 
     
     
         12 . The method of preparing the phosphor according to  claim 1 , wherein the strontium raw material is strontium nitride prepared by firing strontium metal in the atmosphere of nitrogen gas at a firing temperature of 700-900° C., and a firing time for the strontium nitride is 3-24 hours. 
     
     
         13 . The method of preparing the phosphor according to  claim 12 , wherein when preparing the strontium raw material, the method further comprises reducing a heating rate of firing strontium metal when the firing temperature is lower 200° C. than the melting point of strontium metal. 
     
     
         14 . The method of preparing the phosphor according to  claim 12 , wherein when preparing the strontium raw material, a heating rate from a medium temperature to a retained temperature is lower than a heating rate from room temperature to the medium temperature. 
     
     
         15 . The method of preparing the phosphor according to  claim 14 , wherein the medium temperature is 620° C.