Continuous wave and pulsed EPR measurements of chromium-doped fluoro-chlorozirconate and fluoro-bromozirconate glasses

Abstract

A continuous wave (CW) and pulsed electron paramagnetic resonance (EPR) investigation of chromium-doped fluoro-chlorozirconate and fluoro-bromozirconate glasses with different contents of the heaviest halogens is presented. The CW EPR spectra are interpreted by assuming a preferential substitution of the fluoride ions in the first co-ordination shell of the ions by chloride or bromide ions, which is in agreement with previous optical data. Values for the spin Hamiltonian parameters are discussed for different amounts of halide substitution. Pulsed EPR studies are mainly focused on the ESEEM (electron spin echo envelope modulation) signal. It shows the frequency peaks due to fluoride ions and to the corresponding alkali metal cation (Na or Li), which provides information about the bulk structure of the glass and strongly suggests that it is essentially the same as that of the fluorozirconate glasses. ESEEM results indicate that centres are mainly isolated.