OPTICAL-ABSORPTION AND ELECTRICAL RELAXATION IN ALKALINE-EARTH FLUORIDES DOPED WITH URANIUM

This work is concerned with optical absorption and electrical relaxati on studies of calcium, barium, and strontium fluorides containing uran ium up to the 0.5% doping level. The optical absorption spectra indica te the existence of both U4+ and U3+ ions but there is no evidence of any U2+ ions. Each sample exhibits two or more electrical relaxation p eaks. By comparison with previous work on the alkaline earth fluorides containing known tetravalent and trivalent ions, some relaxations can be attributed to trivalent uranium and others to tetravalent uranium and thus both the electrical relaxation and optical absorption data re veal the presence of both U4+ and U3+ ions.