CONTINUOUS-WAVE AND PULSED EPR MEASUREMENTS OF CHROMIUM-DOPED FLUORO-CHLOROZIRCONATE AND FLUORO-BROMOZIRCONATE GLASSES

A continuous wave (CW) and pulsed electron paramagnetic resonance (EPR ) investigation of chromium-doped fluoro-chlorozirconate and fluoro-br omozirconate glasses with different contents of the heaviest halogens is presented. The CW EPR spectra are interpreted by assuming a prefere ntial substitution of the fluoride ions in the first co-ordination she ll of the Cr3+ ions by chloride or bromide ions, which is in agreement with previous optical data. Values for the spin Hamiltonian parameter s are discussed for different amounts of halide substitution. Pulsed E PR studies are mainly focused on the ESEEM (electron spin echo envelop e modulation) signal. It shows the frequency peaks due to fluoride ion s and to the corresponding alkali metal cation (Na or Li), which provi des information about the bulk structure of the glass and strongly sug gests that it is essentially the same as that of the fluorozirconate g lasses. ESEEM results indicate that Cr3+ centres are mainly isolated.