EPR AND OPTICAL ABSORPTION STUDIES OF Mn²⁺ IONS IN ALKALI BOROTELLURITE GLASSES

Abstract

Electron paramagnetic resonance (EPR) and optical absorption spectra of Mn2+ ions in alkali borotellurite glass systems have been studied. The EPR spectra of all the glass samples exhibit three resonance signals at g ≈ 2.0, g ≈ 3.3 and g ≈ 4.3. A six line hyperfine structure has also been observed at g ≈ 2.0. The concentration and temperature dependence of EPR signals were studied for Mn2+ ions in potassium borotellurite glass samples. The zero-field splitting parameter D has been calculated for different alkali borotellurite glass samples from the intensities of the allowed hyperfine lines. The paramagnetic susceptibility was calculated from the EPR data at various temperatures and the Curie constant was calculated from the 1/χ versus T graph. The optical absorption spectrum exhibits a single broad band near 498 nm and this has been attributed to the spin-allowed 5Eg → 5T2g transition of Mn3+ ions in octahedral symmetry. The optical band gap energy (E opt ) and Urbach energy (Δ E) were calculated from their ultraviolet edges. The optical band gap energy varies between 3.38 and 3.61 eV and increases from Li to K glasses.

Induced crystallization and structural aspects of PbO-As2O3 glass system doped with Fe2O3

“…Iron ions have strong bearing on electrical, optical and magnetic properties of glasses. A large number of interesting studies are available on the environment of iron ion in various inorganic glass systems viz., silicate, borate, phosphate, germinate glasses [2][3][4][5][6][7][8][9][10][11] and also in certain tellurite glass systems [12,13]. These ions exist in different valence states with different coordinations in glass matrices, for example as Fe 3+ with both tetrahedral and octahedral and as Fe 2+ with octahedral environment [14,15].…”

“…Fe 2+ has a d 6 electronic configuration, and octahedral complexes with weak field ligands have a high spin arrangement with four unpaired electrons. Fe 3+ has a d 5 electronic configuration and the ground state is 6 S 1/2 in free atom and possesses zero orbital angular momentum. Hence, any magnetic behaviour of Fe 3+ ion is due to its spin only.…”

“…The ground state configuration gives rise to electronic states 6 T 2g , 4 A 2g and to a number of doublet states of which 6 A 1g lies lowest according to Hunds' rule. The optical absorption spectrum is expected to exhibit bands from the ground state 6 A 1g to some quartet states and these are both spin and parity forbidden.…”

“…The optical absorption spectrum is expected to exhibit bands from the ground state 6 A 1g to some quartet states and these are both spin and parity forbidden. Generally, the optical absorption bands of Fe 3+ complexes can be seen in the visible and ultraviolet regions.…”

“…Generally, the optical absorption bands of Fe 3+ complexes can be seen in the visible and ultraviolet regions. In general, 6 A 1g (S) 4 E g (G), 6 A 1g (S) 4 A 1g (G) and 6 A 1g (S) 4 E g (D) bands are sharp as they arise from intraconfigurational transitions. The transitions 6 A 1g (S) 4 T 1g (G) and 6 A 1g (S) 4 T 2g (G) involve a change of configuration from (t 2g ) 3 (e g ) 2 to (t 2g ) 4 (e g ) 1 and are therefore observed to be broad.…”