Defects in U 3+ :CaF 2 single crystals grown under different conditions by the temperature gradient technique

Defects in as‐grown U 3+ :CaF 2 crystals grown with or without PbF 2 as an oxygen scavenger were studied using Raman spectra, thermoluminescence glow curves, and additional absorption (AA) spectra induced by heating and γ‐irradiation. The effects of heating and irradiation on as‐grown U 3+ :CaF 2 crystals are similar, accompanied by the elimination of H‐type centers and production of F‐type centers. U 3+ is demonstrated to act as an electron donor in the CaF 2 lattice, which is oxidized to the tetravalent form by thermal activation or γ‐irradiation. In the absence of PbF 2 as an oxygen scavenger, the as‐grown U 3+ :CaF 2 crystals contain many more lattice defects in terms of both quantity and type, due to the presence of O 2– impurities. Some of these defects can recombine with each other in the process of heating and γ‐irradiation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)