Abstract: Suitable as active cathode material for an electrochemical lithium secondary cell are oxygen-deficient spinels Li1+xMn2−xO4−&dgr; , where 0≦x≦0.33 and 0.01≦&dgr;≦0.5. Their region of existence in a phase diagram laid out between the corner points MnO, MnO2 and Li2MnO3 for lithium manganese oxide compounds is defined by the corner compounds LiMn2O4, Li2Mn4O7, Li8Mn10O21 and Li4/3Mn5/3O4, all the compounds along the lines LiMn2O4—Li4/3Mn5/3O4 and LiMn2O4—Li2Mn2O4 being excepted. The spinels are produced by a modified ceramic process from a mixture of Li-containing and Mn-containing starting substances whose reaction product is reduced by roasting in an Ar/H2 atmosphere. The Li components x can be replaced partially or completely by foreign monovalent or multivalent cations from the series consisting of Co, Mg, Zn, Ni, Ca, Bi, Ti, V, Rh or Cu.

Abstract: Phosphors constituted by terbium and/or cerium activated lutetium-gadolinium-yttrium silicates have shown a high visible-light emission efficiency upon exposure to high energy radiation.Said phosphors are useful in the methods for recording and reproducing high energy radiation images.