Abstract: A glass ceramic material for storing energy of X-rays and releasing said energy by photo-stimulation comprising a fluoride glass matrix containing micro-crystalline particles, said particles having an average particle size, d, so that d<2 &mgr;m and said glass ceramic shows in a XRD spectrum a continuous spectrum of said glass matrix and discrete peaks superimposed on said continuous spectrum. Said glass matrix contains preferably zirconium ions and ions selected from the group consisting of alkali ions and alkaline earth ions, at least 5 mole % of the fluoride ions is replaced by bromide and/or chloride ions and at least 0.01 mole % of cations selected from the group consisting of transition metal ions, rare earth metal ions, In+, Ga+, Tl+, and Pb2+ is present.

Abstract: An elpasolite phosphor is provided corresponding to the general formula: A2−yB1+yMe3+X6:xD wherein: A=a monovalent ion B=a monovalent ion A is different from B Me3+=a trivalent ion D is a dopant X is at least one of F, Cl, Br and I 0≦y≦1 0≦x≦0.2 and wherein said phosphor has a specific gravity (sg)≧4. An elpasolite phosphor corresponding to the general formula above is especially useful in the production of prompt emitting X-ray screens and in the production of X-ray energy storage screens.

Abstract: A radiation image storage screen is provided comprising an alkali metal phosphor wherein the dopant is selected from the group consisting of Ga.sup.1+, Ge.sup.2+, Sn.sup.2+, Sb.sup.3+ and As.sup.3+. In a preferred embodiment the alkali metal is Cs and/or Rb.