Borate oxide glass system of composition 10 KM–64.7 B2O3–25 Na2O–0.3 Cr2O3 (M = Cl, Br and I) was prepared
by conventional melt quenching technique. The amorphous nature of the investigated glasses was
checked by the X-ray diffraction (XRD) technique. The optical basicity of the system has been calculated,
and was found to increase by going from KCl to KBr and to KI. Optical absorption spectra were recorded in
the UV–visible range. Through a careful analysis of the data, the ligand field parameters (crystal field
strength Dq, Racah parameters B and nephelauxetic functions h) and the optical parameters (optical band
gap, Urbach tail band width, and refractive index) have been estimated. The obtained results reveal a
strong correlation between that ligand field parameters and the type of halogen atom; the crystal-field
strength of KCl or KBr samples are very pronounced but it is rather weak in the KI sample. Electron spin
resonance (ESR) has been used to probe the valency of the Chromium ions. The resulting ESR parameters
revealed that chromium ions are predominantly in the trivalent state with traces of hexavalent state.
Using Infrared spectroscopy (IR) information on the boron structural units has been obtained. The N4
ratio increases by replacing the KCl by KBr or KI, and it was found that the tetrahedral coordination of
Cr+ ions becomes preferential in the host glasses with increasing the optical basicity.
Borate oxide glass system of composition 10 KM–64.7 B2O3–25 Na2O–0.3 Cr2O3 (M = Cl, Br and I) was preparedby conventional melt quenching technique. The amorphous nature of the investigated glasses waschecked by the X-ray diffraction (XRD) technique. The optical basicity of the system has been calculated,and was found to increase by going from KCl to KBr and to KI. Optical absorption spectra were recorded inthe UV–visible range. Through a careful analysis of the data, the ligand field parameters (crystal fieldstrength Dq, Racah parameters B and nephelauxetic functions h) and the optical parameters (optical bandgap, Urbach tail band width, and refractive index) have been estimated. The obtained results reveal astrong correlation between that ligand field parameters and the type of halogen atom; the crystal-fieldstrength of KCl or KBr samples are very pronounced but it is rather weak in the KI sample. Electron spinresonance (ESR) has been used to probe the valency of the Chromium ions. The resulting ESR parametersrevealed that chromium ions are predominantly in the trivalent state with traces of hexavalent state.Using Infrared spectroscopy (IR) information on the boron structural units has been obtained. The N4ratio increases by replacing the KCl by KBr or KI, and it was found that the tetrahedral coordination ofCr+ ions becomes preferential in the host glasses with increasing the optical basicity.
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