Precipitation of calcium tungstate-based phosphor with increased luminescence

A method is described of precipitating a phosphor with increased luminescence based on calcium tungstate by the addition of aqueous solutions of (A) tungstate and (B) calcium salt to a third solution (C), this either of tungstate or of calcium salt at intensive stirring. The method is typical of the application of solutions (A) and (B) at concentrations lower than 0.5 mole/l and of solution (C) at a concentration ranging from 1/15 to 1/2 of that of solutions (A) and (B), at a temperature of the mixture low enough to prevent crystal formation from the grains. The grains will be transformed in the crystallic form by heating up the solution. (V.V.)