Process of making tantalate X-ray phosphors

A process of making a tantalate X-ray phosphor selected from the group consisting of:

• (a) YNb.sub.x Ta.sub.1-x O.sub.4, where x=0 to about 01.5;
• (b) LuNb.sub.x Ta.sub.1-x O.sub.4, where x=0 to about 0.2;
• (c) Y.sub.1-y Tm.sub.y TaO.sub.4, where x=0 to about 0.2;
• (d) a solid solution of (a) and (b);
• (e) a solid solution of (a) and (c);
• (f) Y.sub.1--y Tb.sub.y TaO.sub.4, where y= about 0.001 to about 0.15;
• (g) Lu.sub.1--y Tb.sub.y TaO.sub.4, where y= about 0.001 to about 0.15;
• (h) Gd.sub.1--y Tb.sub.y TaO.sub.4, where y= 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) where up to 45 mole percent of the yttrium, lutetium or gadolinium is replaced by lanthanum;
• (k) any of (a ) to (i) wherein up to 45 mole percent of the yttrium, lutetium or gadolinium is replaced by ytterbium;
• and
• (1) any of (a), (b), (c), (d) or (e) wherein up to 15 mole percent of yttrium or lutetium is replaced by gadolinium;
• said process comprising the steps of:
• 1) intimately mixing stoichiometric quantities of precursor oxides for the tantalate X-ray phosphor;
• 2) mixing said mixture with a flux composition consisting of:
• i) 1-99% by weight of at least one alkali metal sulfate,
• ii) 1-99% by weight of at least one alkali metal metaborate, and
• iii) 0-50% by weight of at least one strontium halide;
• and
• 3) firing the flux-containing mixture for a sufficient period of time and at a sufficient temperature to form the tantalate X-ray phosphor from the precursor oxides.