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The advances of EPR spectroscopy for the detection of activators as well as determining their local structure in the crystalline phase of glass ceramics is considered. The feasibility of d-element (Mn 2+ , Cu 2+ ) and f-element (Gd 3+ , Eu 2+ ) ion probes for the investigation of glass ceramics is discussed. In the case of Mn 2+ , the information is obtained from the EPR spectrum superhyperfine structure, for Gd 3+ and Eu 2+ probes -from the EPR spectrum fine structure, whereas for Cu 2+ ions the changes in the EPR spectrum shape could be useful. The examples of EPR spectra of the above-mentioned probes in oxyfluoride glass ceramics are illustrated. PACS: 76.30.-v Electron paramagnetic resonance and relaxation; 61.72.Hh Indirect evidence of dislocations and other defects.

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We studied EPR spectra of pure LiBaF3 sample of high quality. For EPR measurements LiBaF3 sample was X‐irradiated at room temperature, however spectra could be observed at low temperatures ‐ at 77 K. All hyperfine structure lines of F‐type centre could be well resolved contrary to our earlier studies of Fe doped LiBaF3 crystal. Qualitative analysis with g‐tensor parameters derived from magneto‐optical measurements showed that the F‐type centre observed earlier by MCD‐EPR techniques is the same F‐type centre we observe with the EPR. We analyse origin of the hyperfine structure of the EPR spectra and their angular dependencies and discuss the structure of F‐type centres in the LiBaF3 crystal. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)