Magnesium barium thioaluminate and related phosphor materials

Abstract

A phosphor and a method of deposition. The phosphor comprises a composition of the formula M′ a Ba 1-a M″ 2 M′″ 4′ :RE, where M′ is at least one element selected from magnesium and calcium, M″ is at least one element selected from aluminum, gallium and indium, M′″ is at least one element selected from sulphur, selenium and tellurium, RE is at least one rare earth element, especially europium or cerium, and 0<a<1. Deposition is preferably by dual source electron beam deposition. The phosphor may be annealed. The phosphor provides a high luminosity blue emission that does not require an optical filter to achieve acceptable colour coordinates for the blue sub-pixel element for a full colour thin film or thick film electroluminescent display. The blue sub-pixel pixel performance meets the luminosity and colour temperature specifications for current generation cathode ray tube displays.

1 . A phosphor comprising a composition of the formula M′ a Ba 1-a M″ 2 M′″ 4′ :RE, where 
 M′ is at least one element selected from the group consisting of magnesium and calcium,  
 M″ is at least one element selected from the group consisting of aluminum, gallium and indium,  
 M′″ is at least one element selected from the group consisting of sulphur, selenium and tellurium,  
 RE is at least one rare earth element, and  
 0<a<1.  
 
     
     
         2 . The phosphor of  claim 1  in which the phosphor has been annealed.  
     
     
         3 . The phosphor of  claim 1  in the form of a phosphor in a thick film electroluminescent display.  
     
     
         4 . The phosphor of  claim 3  in which M″ is aluminum.  
     
     
         5 . The phosphor of  claim 4  in which RE is europium.  
     
     
         6 . The phosphor of  claim 4  in which M′″ is sulphur.  
     
     
         7 . The phosphor of  claim 6  in which M′ is magnesium, M′″ is sulphur and RE is europium.  
     
     
         8 . The phosphor of  claim 7  in which “a” is in the range of 0.4 to 0.8.  
     
     
         9 . The phosphor of  claim 7  in which “a” is in the range of 0.4 to 0.8, said phosphor comprising a eutectic composition.  
     
     
         10 . The phosphor of  claim 7  in which “a” is in the range of 0.7 to 0.8.  
     
     
         11 . The phosphor of  claim 1  in the form a phosphor in a thin film electroluminescent display.  
     
     
         12 . A method for the preparation of a phosphor on a substrate, said phosphor comprising a composition of the formula M′ a Ba 1-a M″ 2 M′″ 4 :RE, where 
 M′ is at least one element selected from the group consisting of magnesium and calcium,  
 M″ is at least one element selected from the group consisting of aluminum, gallium and indium,  
 M′″ is at least one element selected from the group consisting of sulphur, selenium and tellurium,  
 RE is at least one rare earth element, and  
 0<a<1,  
 said method comprising using a compound of the formula M″ 2 M′″ 3  as a first source in a dual source electron beam evaporation apparatus and using a mixture of compounds of the formulae M′M′″ and BaM′″ as a second source in said apparatus, said compound of the first source and said compounds of the second source being in the ratios to provide a composition of the phosphor and at least one of the first and second sources including a compound of the formula REM′″, and  
 effecting electron beam evaporation from said first and second sources to a substrate to be coated with said phosphor.  
 
     
     
         13 . The method of  claim 12  in which the phosphor so obtained is annealed.  
     
     
         14 . The method  claim 12  in which the substrate is for a thick film electroluminescent display.  
     
     
         15 . The method of  claim 14  in which M″ is aluminum.  
     
     
         16 . The method of  claim 14  in which RE is europium.  
     
     
         17 . The method of  claim 14  in which M′″ is sulphur.  
     
     
         18 . The method of  claim 14  in which M′ is magnesium, M′″ is sulphur and RE is europium.  
     
     
         19 . The method of  claim 18  in which “a” is in the range of 0.4 to 0.8.  
     
     
         20 . The method of  claim 18  in which “a” is in the range of 0.4 to 0.8, and the phosphor obtained is comprised of a eutectic composition.  
     
     
         21 . The method of  claim 18  in which “a” is in the range of 0.7 to 0.8.  
     
     
         22 . The method of  claim 18  in which the phosphor is annealed at a temperature of at least about 850° C.  
     
     
         23 . The method of  claim 18  in which the phosphor is annealed at a temperature of at least about 600° C.  
     
     
         24 . The method of  claim 18  in which RE is europium in an amount of not more than 3 atomic percent, based on the amount of M′ and barium.  
     
     
         25 . The method of  claim 24  in which REM′″ is europium sulphide.  
     
     
         26 . The method of  claim 25  in which the europium sulphide is replaced in whole or in part with europium oxide.  
     
     
         27 . The method of  claim 12  in which the substrate is for a thin film electroluminescent display.