EFFECTS OF PHASE-SEPARATION AND DEVITRIFICATION PROCESSES IN OXIDE GLASSES ON ESR-SPECTRA

The consequences of phase separation and devitrification processes for the ESR patterns of Fe3+ ions and oxygen hole centres in glassy and g lassy-crystalline systems are discussed. Analysis of the Fe3+ spectra by simulation (including 4th order terms) allows their model-based int erpretation for homogeneous, phase-separated and devitrified samples a s well. It is even possible to estimate the ratio of Fe3+ ions incorpo rated into the glassy matrix to those localized in the crystalline pha se. An influence of irreversible structural reorganization in glasses on gamma-irradiation-induced oxygen hole centres is detectable by stud ying their saturation behaviour. For the example of a barium silicate glass studied here, pronounced passage effects could be detected at 77 K. In contrast, a devitrified sample of the same composition after ga mma irradiation yielded the same spectral pattern at low microwave pow er, but only saturation broadening was to be observed when rising the microwave power. In an annealed sample of anorthite composition (in mo l%: 25CaO, 25Al(2)O(3), 50SiO(2)) progressive crystal growth was detec table using Fe3+ ions as probes.