Photoelectron spectroscopy study of iron sodium tellurite glasses

Iron sodium tellurite glasses with nominal composition xFe ₂O₃-0.3Na₂O-(0.7-x) TeO₂, where 0.05≤x≤0.15, have been prepared by a melt quenching technique. The core level spectra of Fe 2p, Te 3d and O 1s were recorded and analysed. The Fe 2p_3/2 core level peak has the same binding energy at ∼710 eV for all samples. The energy separation between the Fe 2p_1/2 and the Fe 2p_3/2 spin orbit doublet is found to be constant, having a value of ∼13.5 eV on average for all glass compositions. Curve fitting of Fe 2p spectra revealed that Fe is predominantly in the Fe³⁺ state. The energy separation between the Te 3d spin orbit doublet spectra is ∼10.4 eV, while the binding energy of the Te 3d_5/2 is found to be ∼576 eV. However, the full width at half maximum increases with increase in x, which suggests the existence of at least two types of Te atoms sites. The Te 3d _5/2 peak was fitted with two contributions, one from Te ions in TeO₃ units and the other from Te ions in TeO₄. The proportion of TeO₃ units increases with increase in Fe ₂O₃ content. There is a slight decrease in the binding energy of the O 1s spectra while the FWHM of the peaks is seen to increase with increase in Fe₂O₃ content indicating the possibility of more than one contribution to the O 1s peaks. The spectra were fitted with two contributions, one from bridging oxygen (BO) due to oxygen atoms in the configuration Te-O-Te and the other from nonbridging oxygen atoms (NBO) due to oxygen atoms in the configuration Te-O-Fe(III) and Te-O-Na⁺. The number of NBO was found to increase with increase in Fe₂O₃ content.