3. Results and discussion
3.1. Transition metal ions (Cr3+)
Excited state relaxation of trivalent Cr3+ ions in different glassy and crystalline solid-state materials was reviewed [9]. Especially, spectral lines of Cr3+ in oxide [10–12] and non-oxide [13–15] glasses were analyzed. The detailed study indicates that chromium ions can occupy low-field and high-field sites [16]. It is also well noted from the previously published results based on absorption and luminescence spectra, that chromium at different valence states such as Cr3+, Cr4+, Cr5+ and Cr6+ can be exist in the glass. The spectral analysis suggests that the chromium at its low concentration exist in Cr3+ state, which act as modifiers. When Cr2O3 is present in higher concentrations in the glass matrix, these ions seem to exist in Cr6+ state and take part in network forming positions with CrO2−4 structural units in PbO–Al2O3–B2O3 glass systems [17]. It proves data obtained from electron paramagnetic resonance (EPR) measurements.
The EPR spectra exhibit two resonance signals at g = 4.65 and 1.97 for chromium in alkali lead borotellurite glasses [18] and g = 4.50 and 1.98 for chromium in alkaline earth alumino borate
ones [19], which can be attributed to Cr3+ and Cr5+ ions, respectively.
3. Results and discussion3.1. Transition metal ions (Cr3+)Excited state relaxation of trivalent Cr3+ ions in different glassy and crystalline solid-state materials was reviewed [9]. Especially, spectral lines of Cr3+ in oxide [10–12] and non-oxide [13–15] glasses were analyzed. The detailed study indicates that chromium ions can occupy low-field and high-field sites [16]. It is also well noted from the previously published results based on absorption and luminescence spectra, that chromium at different valence states such as Cr3+, Cr4+, Cr5+ and Cr6+ can be exist in the glass. The spectral analysis suggests that the chromium at its low concentration exist in Cr3+ state, which act as modifiers. When Cr2O3 is present in higher concentrations in the glass matrix, these ions seem to exist in Cr6+ state and take part in network forming positions with CrO2−4 structural units in PbO–Al2O3–B2O3 glass systems [17]. It proves data obtained from electron paramagnetic resonance (EPR) measurements.The EPR spectra exhibit two resonance signals at g = 4.65 and 1.97 for chromium in alkali lead borotellurite glasses [18] and g = 4.50 and 1.98 for chromium in alkaline earth alumino borateones [19], which can be attributed to Cr3+ and Cr5+ ions, respectively.
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