Process of preparing tantalate X-ray intensifying phosphors with improved efficiency

Claim 1

A process for preparing a phosphor with improved X-ray efficiency and purity prepared from a tantalate phosphor having the monoclinic M' structure selected from the group consisting of: (a) YNb x Ta 1-x O 4 , where x is 0 to about 0.15; (b) LuNb x Ta 1-x O 4 , where x is 0 to about 0.20; (c) Y 1-y Tm y TaO 4 , where y is 0 to about 0.03; (d) a solid solution of (a) and (b); (e) a solid solution of (a) and (c); (f) Y 1-y Tb y TaP 4 , where y is about 0.001 to about 0.15; (g) Lu 1-y Tb y TaO 4 , where y is about 0.001 to about 0.15; (h) Gd 1-y Tb y TaO 4 , where y is about 0.001 to about 0.15; (i) a solid solution of at least two of (f), (g) and (h); (j) any of (a) to (i) wherein up to 45 mole percent of the yttrium, lutetium or gadolinium is replaced by lanthanum; (k) any of (a) to (i) wherein up to 15 mole percent of the yttrium, lutetium or gadolinium is replaced by ytterbium; and (l) any of (a), (b), (c), (d) and (e) wherein up to 15 mole percent of the yttrium or lutetium is replaced by gadolinium; the process comprising (a) intimately mixing stoichiometric quantities of corresponding precursor oxides; (b) mixing the resultant mixture with a flux capable of producing an alkali metal oxide wherein said flux also contains an effective amount of an alkali metal metasilicate; (c) firing the flux-containing mixture in an inert container in the range of about 1100° C. to about 1400° C. for at least about 3 hours; and (d) recovering the phosphor.