Preparation of BaFCl:Eu phosphors

Claim 2

A process for preparing a europium doped BaFCl phosphor comprising: (a) preparing an intimate mixture consisting essentially of particles of BaFCl having a MSED less than 2 microns, a europium source which is selected from the class consisting of EuCl 3 , EuCl 2 , EuF 2 , EuF 3 , BaFCl:Eu, and Ba 7 Eu 6 F 32 and about 0.1-25 percent by weight, based on the weight of BaFCl, of a chloride flux of at least one water-soluble chloride selected from the group consisting of alkali metal chlorides and alkaline earth metal chlorides, (b) firing said mixture in an inert atmosphere at a temperature in the range of about 550°-900° C and above the liquid temperature of the flux of a time sufficient to effect reaction of europium with the BaFCl including the reduction of any Eu 3+ to Eu 2+ and diffusion of europium throughout the phosphor, and (c) washing the fired product with water to remove the chloride flux.

Claim 3

The process of claim 1 wherein the flux is at least one of KCl, NaCl, LiCl, CaCl 2 , BaCl 2 , SrCl 2 , and MgCl 2 .

Claim 4

The process of claim 2 wherein the firing temperature is in the range of about 600°-880° C.

Claim 5

The process of claim 3 wherein the chloride flux concentration is about 0.1-10 percent by weight.

Claim 6

The process of claim 3 wherein the flux is a mixture of BaCl 2 , CaCl 2 and KCl or a mixture of BaCl 2 and KCl.

Claim 7

The process of claim 3 wherein the intimate mixture is prepared by slurrying the BaFCl particles and Eusource particles in an aqueous solution of the chloride flux and then removing the water.

Claim 8

The process of claim 1 wherein the BaFCl is prepared by forming a slurry consisting of an aqueous solution of BaCl 2 and solid BaF 2 with the amount of BaCl 2 being in excess of the stoichiometric amount needed to form BaFCl and agitating the resulting slurry for a time sufficient to allow the solid BaF 2 to be replaced by particles of BaFCl.

Claim 9

The process of claim 7 wherein an aqueous solution of a water-soluble europium source is added to the precipitated BaFCl to form a slurry.

Claim 10

The process of claim 8 wherein the water-soluble europium source is EuCl 3 .

Claim 11

The process of claim 8 wherein at least one water-soluble chloride flux selected from the group consisting of KCl, NaCl, LiCl, CaCl 2 , BaCl 2 , SrCl 2 , and MgCl 2 is added to the aqueous slurry containing the particles of BaFCl and the europium source.

Claim 12

The process of claim 1 wherein the time of firing is in the range of 5 to 60 minutes.

Claim 13

A process for preparing a europium doped BaFCl phosphor comprising: (a) forming a slurry consisting essentially of an aqueous solution of BaCl 2 and solid BaF 2 with the amount of BaCl 2 being about 0.5-100 mole percent in excess of the stoichiometric amount needed to form BaFCl, agitating the resulting slurry for a time sufficient to allow the BaF 2 to be replaced by particles of BaFCl, said particles having a MSED less than 2 microns, and removing sufficient H 2 O or BaCl 2 solution to entrain excess BaCl 2 with the BaFCl particles, (b) intimately mixing a europium source which is selected from the class consisting of EuCl 3 , EuCl 2 , EuF 2 , EuF 3 , BaFCl:Eu and Ba 7 EU 6 F 32 with the BaFCl, (c) drying the mixture, (d) firing the dried mixture in a nitrogen atmosphere at a temperature in the range of about 550°-900° C for a time sufficient to effect reaction of europium with the BaFCl including the reduction of any Eu 3+ to Eu 2+ and diffusion of europium throughout the phosphor, and (e) washing the fired product with water to remove excess BaCl 2 .

Claim 14

A process for preparing a europium doped BaFCl phosphor comprising: (a) forming a slurry consisting essentially of an aqueous solution of BaCl 2 and solid BaF 2 with the amount of BaCl 2 being about 0.5-100 mole percent in excess of the stoichiometric amount needed to form BaFCl, agitating the resulting slurry for a time sufficient to allow the BaF 2 to be replaced by particles of BaFCl, said particles having a MSED less than 2 microns, and removing sufficient H 2 O or BaCl 2 solution to entrain excess BaCl 2 with the BaFCl particles, (b) intimately mixing a europium source which is selected from the class consisting of EuCl 3 , EuCl 2 , EuF 2 , EuF 3 , BaFCl:Eu and Ba 7 EU 6 F 32 with the BaFCl, (c) drying the mixture, (d) firing the dried mixture in a nitrogen atmosphere at a temperature in the range of about 550°-900° C for a time sufficient to effect reaction of europium with the BaFCl including the reduction of any Eu 3+ to Eu 2+ and diffusion of europium throughout the phosphor, and (e) washing the fired product with water to remove excess BaCl 2 .

Claim 15

The process of claim 12 wherein the europium source is EuCl 3 in aqueous solution.

Claim 16

The process of claim 12 wherein about 0.1-25 percent by weight, based on the weight of BaFCl, of at least one water-soluble chloride in aqueous solution is added to the europium source-BaFCl mixture, said chloride selected from the group consisting of KCl, NaCl, LiCl, BaCl 2 , CaCl 2 , SrCl 2 and MgCl 2 .

Claim 17

The process of claim 14 wherein the added chloride is a mixture of CaCl 2 , KCl, and BaCl 2 , or a mixture of BaCl 2 and KCl.

Claim 18

The process of claim 13 wherein about 0.1-25 percent by weight, based on the weight of BaFCl, of at least one water-soluble chloride in aqueous solution is added to the mixture of the europium source and BaFCl, said chloride selected from the group consisting of KCl, NaCl, LiCl, BaCl 2 , CaCl 2 , SrCl and MgCl 2 .

Claim 19

The process of claim 16 wherein the added chloride is a mixture of CaCl 2 , KCl and BaCl 2 or a mixture of BaCl 2 and KCl.

Claim 20

The process of claim 12 wherein the time of firing is in the range of 5 to 60 minutes.