Gamma-ray induced reduction of W⁶⁺ into W⁵⁺ in the Na₂O -WO₃ glasses

Abstract

The ESR spectra of the 38Na₂O · 62WO₃ glasses irradiated with the⁶⁰Co γ-rays of 10⁵–10⁶ Gy comprised a broad singlet peak (g=1.65, ΔH _pp=28.6 mT), a narrow singlet (g=2.00₁, ΔH _pp=1.36 mT), and a narrow doublet (g=2.00₁, ΔH _pp=0.72 mT,A=4.96 mT). The broad singlet and the two narrow peaks were respectively ascribed to the W⁵⁺ and the W-OHC (oxygen hole center) produced by the γ-ray irradiation. TheΘ _D (360 K) andΘ _E (180 K), obtained from the low-temperature¹¹⁹Sn-Mössbauer measurement of 38Na₂O · 61WO₃·SnO₂ glass, indicated that octahedral Sn⁴⁺ substituted for octahedral W⁶⁺ and played a role of network former (NWF). A gradual increase in the isomer shift (δ) from −0.02 to 0.09 mm s⁻¹ was observed with an increasing γ-ray dose, due to the charge transfer from oxygen to the Sn⁴⁺.