Optical absorption and EPR spectroscopic studies of (30- x) Li_2O-xK_2O-10CdO-59B_2O_3-1Fe_2O_3: An evidence for mixed alkali effect

摘要

Optical absorption and EPR spectroscopic studies were carried on (30- x) Li_2O-xK_2O-10CdO-59B_2O_3-1Fe_2O_3-1Fe_2O_3 (x = 0-30) glass system to understand the effect of progressive doping of Li~+ ion with K~+ ion. Optical absorption results show typical spectra of Fe~(3+) ions and the various optical parameters such as, optical band gap, Urbach energy, oxide ion polarizability, optical basicity and interaction parameter were evaluated from the experimental data. The observed optical band gap and Urbach energy values show large deviation from the linearity where as the other parameters show small deviation from the linearity with the progressive substitution of Li~+ ions with K~+ ions. The observed EPR spectra are representative of Fe~(3+) ion in octahedral and axial fields in the glass network. The number of paramagnetic centers and paramagnetic susceptibility values were evaluated at different resonance lines for all the specimens and these parameters show non-additive nature with the progressive substitution of Li~+ ions with K~+ ions in the glass network. This is first ever observation of mixed alkali effect (MAE) in EPR and optical parameters of mixed alkali borate glasses.