BaFCl:Eu2 + , A NEW PHOSPHOR FOR X-RAY INTENSIFYING SCREENS.

A number of phosphors for X-ray-intensifying screens have been evaluated by calculating figures of merit when used in combination with standard ( ″blue″ -sensitive) X-ray film, BaFCl:Eu**2** plus and BaFBr:Eu**2** plus give better performance than the traditional CaWO//4 and more recently developed UV- or blue-emitting materials (e. g. sulphates and y-oxysulphides). The calculated figures of merit of BaFCl:Eu**2** plus or BaFBr:Eu**2** plus /standard-film combinations are comparable to those of Gd//2O//2S:Tb/green-sensitive X-ray film systems. The preparation of optimal fluorohalide:Eu**2** plus phosphors involves proper formation of the host lattice, complete reduction of Eu**3** plus ions as well as elimination of afterglow. Measurements on powders and experimental screens indicate that, by using BaFCl:Eu**2** plus screens in radiography, important dose reductions can be achieved without the necessity of using other than standard ( ″blue″ -sensitive) X-ray films.