X-ray luminescent screen

Claim 2

An X-ray image intensifier screen comprising a substrate a surface of which is coated with a layer of a bivalent europium activated alkaline earth metal samarium fluoro-halide phosphor of the formula: Me 1-p-q Eu p Sm q FX wherein Me is at least one metal selected from the group consisting of barium, strontium and calcium with the proviso that only up to 20 mol % of Me is calcium, X is at least one halogen selected from the group consisting of chlorine, bromine and iodine and 0.001 ≦ p ≦0.20, 0.0001 ≦ q ≦0.10 and 0.02 ≦ q/p≦0.50

Claim 3

Luminescent screen as claimed in claim 1, characterized in that 0.01 ≦ p ≦ 0.10 0.001 ≦ q ≦ 0.02

Claim 4

Luminescent screen as claimed in claim 2, characterized in that Me is mainly barium and X is mainly chlorine.

Claim 5

A bivalent europium activated alkaline earth metal samarium fluorohalide phosphor of the formula: Me 1-p-q Eu p Sm q FX wherein Me is at least one metal selected from the group consisting of barium, strontium and calcium with the proviso that only up to 20 mol % of Me is calcium, X is at least one halogen selected from the group consisting of chlorine, bromine and iodine and 0.001 ≦ p ≦ 0.20 0.0001 ≦ q ≦ 0.10 and 0.02 ≦ q/p ≦ 0.50

Claim 6

A bivalent europium activated alkaline earth metal samarium fluorohalide phosphor of the formula: Me 1-p-q Eu p Sm q FX wherein Me is at least one metal selected from the group consisting of barium, strontium and calcium with the proviso that only up to 20 mol % of Me is calcium, X is at least one halogen selected from the group consisting of chlorine, bromine and iodine and 0.001 ≦ p ≦ 0.20 0.0001 ≦ q ≦ 0.10 and 0.02 ≦ q/p ≦ 0.50

Claim 7

A method of preparing the phosphor of claim 4 comprising: preparing an aqueous suspension of MeF 2 , 1 mol of MX 2 is dissolved form per mol of MeF 2 , and europium and samarium in the forms of europium halide and samarium halide respectively in amounts at most equal to that desired in said phosphor evaporating the resultant suspension to dryness by heating said suspension at a temperature of 50° to 250° C, mixing the resultant product with amounts of europium halide and samarium halide required to produce said phoshor having the desired amount of europium and samarium, if the amount of europium and samarium in said suspension are less than said desired amount subjecting the resultant mixture to a heat treatment of 600° C to 1000° C in a weakly reducing atmosphere, cooling the reaction product and then finally heating the resultant product at 600° C to 850° C in an inert or weakly reducing atmosphere.