Rare earth activated lanthanum and lutetium oxy-chalcogenide phosphors

Abstract

A family of cathodoluminescent phosphors which consist essentially of oxy-chalcogenides of lanthanum and/or lutetium containing, for each mol of phosphor, between 0.0002 and 0.2 mol of dysprosium, erbium, europium, holmium, neodymium, praseodymium, samarium, terbium, or thulium. Up to 15 mol percent of the lanthanum and lutetium may be replaced with yttrium or gadolinium. The phosphors may be prepared by reacting the constituent elements as compounds thereof at temperatures between 900 and 1300° C. for 0.2 to 5.0 hours and then cooling the reaction product.

I claim: 
     
       1. A phosphor consisting essentially of an oxy-chalcogenide of at least one member of the group consisting of lanthanum and lutetium wherein up to .Badd..[.25.]..Baddend. .Iadd.15 .Iaddend.mol percent of said lanthanum and lutetium is replaced with yttrium or gadolinium, said phosphor containing, for each mol of said phosphor, between 0.0002 and 0.2 mol of a member of the group consisting of dysprosium, erbium, europium, holmium, neodymium, praseodymium, samarium, terbium, and thulium. 
     
     
       2. A phosphor according to claim 1 consisting essentially of a lanthanum oxy-sulfide containing between 0.0002 and 0.2 mol of europium per mol of said phosphor. 
     
     
       3. A phosphor according to claim 1 consisting essentially of a lutetium oxy-sulfide containing between 0.0002 and 0.2 mol europium per mol of said phosphor. 
     
     
       4. A luminescent material whose empirical formula is       M'.sub.(2-x) M".sub.x O.sub.2 CH                                      
     where: M' is at least one member of the group consisting of La and Lu, M" is a member of the group consisting of Dy, Er, Eu, Ho, Nd, Pr, Sm, Tb, and Tm, O is oxygen, Ch is at least one member of the group consisting of S, Se, and Te, and x is between 0.0002 and 0.2.   
     
     
       5. A luminescent material according to claim 4 whose empirical formula is       La.sub.(2-x) M".sub.x O.sub.2 S                                       
     where: La is lanthanum, M" is a member of the group consisting of Dy, Er, Eu, Ho, Nd, Pr, Sm, Tb, and Tm, O is oxygen, S is sulfur, and x is between 0.0002 and 0.2.   
     
     
       6. A luminescent material according to claim 5 having the empirical formula:       La.sub.(2-x) Eu.sub.x O.sub.2 S                                       
     where x is between 0.0002 and 0.2.   
     
     
       7. A luminescent material according to claim 5 having the empirical formula:       La.sub.(2-x) Pr.sub.x O.sub.2 S                                       
     where x is between 0.0002 and 0.2.   
     
     
       8. A luminescent material according to claim 5 having the empirical formula:       La.sub.(2-x) Nd.sub.x O.sub.2 S                                       
     where x is between 0.0002 and 0.2.   
     
     
       9. A luminescent material according to claim 4 whose empirical formula is       Lu.sub.(2-x) M".sub.x O.sub.2 S                                       
     where: Lu is lutetium, M" is at least one member of the group consisting of Dy, Er, Eu, Ho, Nd, Pr, Sm, Tb, and Tm, O is oxygen, S is sulfur, and x is between 0.0002 and 0.2.   
     
     
       10. A luminescent material according to claim 9 having the empirical formula:       Lu.sub.(2-x) Tb.sub.x O.sub.2 S                                       
     where x is between 0.0002 and 0.2.   
     
     
       11. A luminescent material according to claim 9 having the empirical formula:       Lu.sub.(2-x) Eu.sub.x O.sub.2 S                                       
     where x is between 0.0002 and 0.2.   
     
     
       12. In a method for preparing a phosphor whose empirical formula is       M'.sub.(2-x) M'.sub.x O.sub.2 Ch                                      
     where: M' is at least one member of the group consisting of La and Lu and wherein up to about .Badd..[.25.]..Baddend. .Iadd.15 .Iaddend.mol percent of the lanthanum and lutetium is replaced with yttrium and/or gadolinium; M" is a member of the group consisting of Dy, Er, Eu, Ho, Nd, Pr, Sm, Tb and Tm; O is oxygen; Ch is at least one member of the group consisting of S, Se, and Te; and x is between 0.0002 and 0.2; the steps comprising reacting M, M", Ch and O in the form of compounds thereof at temperatures between 900 and 1300° C. for 0.2 to 2.0 hours, thereby forming said phosphor, and then cooling said phosphor.