Properties and structural features of iron doped BABAL glasses

Abstract

The chemical durability, density and structure of the BABAL glasses with batch compositions (100-x)(0.30BaO·0.50B 2 O 3 ·0.20Al 2 O 3 )·xFe 2 O 3 (1 ≤ x ≤ 10 mol%), were investigated using Mössbauer spectroscopy, electron paramagnetic resonance (EPR), X-ray diffraction, Raman and differential thermal analysis (DTA). The chemical durability for the glass of composition 27BaO·45B 2 O 3 ·18Al 2 O 3 ·10Fe 2 O 3 (mol%) at 90 °C in distilled water was 700 times lower than that of iron phosphate glass 40Fe 2 O 3 ·60P 2 O 5 (mol%). The Mössbauer spectra indicate the presence of iron (II) and iron (III) in tetrahedral or octahedral coordination. The results obtained from the g ef = 4.3 EPR line are typical of the occurrence of iron (III) occupying substitutional sites and the line g ef = 2.0 is related to the association of two or more Fe ions found in the interstices (or holes occupied by the glass modifier cations) of the glass network. The paths of X-ray diffraction are typical for glasses based in borate glasses. The Raman spectra showed that the boroxol ring disappears with the increase of iron content, concomitant with the appearance of BO 4 and tetraborate structural units. At these conditions, an increase of dissolution rate and clustering of iron ions is observed.

Electrochemical and structural properties of Ni(II)-alumina composites as an annealing temperature function

“…This signal decreased with the increase of Ni +2 content in Ni-doped alumina indicating that the surrounding of Fe 3+ ion was changed. Similar decrease of signal intensity was noticed in glass matrix with the increase of iron content [27,28]. The decrease was ascribed to the decrease of amount of isolated iron ions due to the increased density of paramagnetic ions.…”

Structural features of iron‐phosphate glass

“…The disappearance in the glasses, containing a relative amount of Fe 2 O 3 ≥8 mol%, of the characteristic g=4.3 resonance line of the isolated Fe 3+ ion was already described in a previous work . The present g=2.0 feature is assigned to a FMR of Fe ions precipitates of ferro‐ or anti‐ferromagnetic single domains encountered in fine‐grained precipitates in glasses where this g=2.0 absorption line also appears when iron ions (Fe 2+ or Fe 3+ ) dimmers or clusters are present at the interstitial positions …”

Al/Fe isomorphic substitution versus Fe2O3 clusters formation in Fe-doped aluminosilicate nanotubes (imogolite)

“…These data are consistent in all cases with Fe centres in the 3? oxidation state (Fallet et al 2003;Lopez et al 2002;Papaefthymiou et al 2002;Reis et al 2003), ruling out the presence of Fe 2?…”