Time-resolved spectroscopy of Ni-doped fluorozirconate glasses

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

“…Following previous studies [11,14] that point to a glass structure in which it is mainly the fluoride ions co-ordinated to chromium that are substituted by chloride or bromide ions, we consider the spectra corresponding to heavily substituted glasses (figures 1(a), 1(e) and 2(e)) as arising from samples in which chromium is co-ordinated only octahedrally, with the six corners occupied by one kind of anion (F − in the fluorozirconate glass and Cl − and Br − in the corresponding mixed glasses). Optical spectroscopy studies performed by Buñuel et al [12,13] are in agreement with this interpretation. The mentioned studies also indicate that in all the other mixed glasses the Cr 3+ neighbourhoods are octahedral and combine different numbers of fluoride and substitute halide ions, then the EPR spectra can be considered as a superposition of signals from Cr 3+ in these different environments.…”

“…Using the perturbative standard analysis of the magnetic properties of an orbital singlet in an intermediate crystal field [20] and assuming that δ , in agreement with the optical properties analysis [12,13], it is found that…”

“…As a final comment on the CW EPR of Cr 3+ in these mixed halide glasses it would be interesting to compare the changes of the most probable values of the zero-field parameter, D, when fluoride ions are substituted by chloride or bromide ions, with the corresponding modifications of the optical properties [12,13].…”

“…On the other hand, it has been found that the refractive index increases as a consequence of the incorporation of more polarizable anions [6]. In addition, the optical properties of the active ions (rare earths or 3d ions) are greatly affected, opening a new way for the preparation of glasses with promising applications [10][11][12][13].…”

“…In particular, the optical properties (absorption, emission and lifetime measurements) of Cr 3+ , Ni 2+ and Mn 2+ in fluoro-chlorozirconate and fluoro-bromozirconate glasses have been studied in our laboratory. The changes in the optical properties associated with the 3d ion as a function of chlorine or bromine content are interpreted assuming that the metal forms hexaco-ordinate complexes and the heavier halides preferentially occupy a neighbouring site to the active impurity in such a way that the optical properties of the doped glasses are due to the existence of metal ions co-ordinated to n F − and (6 − n) X − (X = Cl or Br) where n can be 6, 5, 3, 1, 0 [11][12][13]. Extended x-ray absorption fine structure (EXAFS) studies [14] of the nickel environment in fluoro-chlorozirconate glasses confirm this interpretation.…”