Diluted Fe3+ in silicate glasses: Structural effects of Fe-redox state and matrix composition. An optical absorption and X-band/Q-band EPR study

Vincent Vercamer (1, 2) , Gérald Lelong (1) , Hiroyuki Hijiya (3) , Yuki Kondo (3) , Laurence Galoisy (1) , Georges Calas (1)

1 IMPMC - Institut de minéralogie, de physique des matériaux et de cosmochimie
2 AGC FRANCE
3 Research Center, Asahi Glass Co. Ltd, 1150 Hazawa-cho, Yokohama 221-8755, Japan University College London

Sodium-alkaline earth-silicate glasses, of nominal molar composition 16Na 2 O–10RO–74SiO 2 (R = Ca, (Ca,Mg) and Mg) doped with 0.5 wt% of Fe 2 O 3 , were studied by UV–Visible–NIR absorption spectroscopy and electron paramagnetic resonance (EPR) at X-and Q-band to understand the structural control of Fe 3+ optical absorption properties as a function of iron redox and glass composition. By comparing with a set of [4] Fe 3+ , [5] Fe 3+ and [6] Fe 3+ crystalline references, optical absorption spectra indicate the presence of 5-fold Fe 3+ in addition to a majority of tetrahedral Fe 3+. The combination of Q-and X-band EPR data shows Fe 3+ partition among isolated, distributed sites and Fe-rich clusters, providing unique insight into the distortion of isolated Fe 3+ sites. It demonstrates also the peculiar character of the residual Fe 3+ sites that exist in reduced glasses. Changing Ca to Mg increases the amount of tetrahedral Fe 3+ sites and decreases their distortion. The presence of Mg also reduces the amount of isolated rhombic Fe 3+ sites and promotes the formation of clusters. These clusters confirm the non-homogeneous structure of silicate glasses, as well as the preference of Fe 3+ for a more calcic than magnesian environment in sodic (Ca,Mg) glasses.

Mots clés: iron redox; clustering; optical absorption spectroscopy

Domaines: Biophysique; Physique [physics]

Vincent Vercamer, Gérald Lelong, Hiroyuki Hijiya, Yuki Kondo, Laurence Galoisy, et al.. Diluted Fe3+ in silicate glasses: Structural effects of Fe-redox state and matrix composition. An optical absorption and X-band/Q-band EPR study. Journal of Non-Crystalline Solids, 2015, pp.138-145. ⟨10.1016/j.jnoncrysol.2015.08.010⟩. ⟨hal-01198781⟩