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$Fe^{3+}$ ions in alkali lead tetraborate glasses-an electron paramagnetic resonance and optical study
Title:
$Fe^{3+}$ ions in alkali lead tetraborate glasses-an electron paramagnetic resonance and optical study
Archive:
Eprints@iisc
Author(s):
Chakradhar, Sreekanth RP
Sivaramaiah, G
Rao, Lakshmana J
Gopal, NO
Sivaramaiah, G
Rao, Lakshmana J
Gopal, NO
Date:
2005-11-01
Abstract:
Glass systems of composition $90R_{2}B_{4}O_{7} + 9PbO + 1Fe_{2}O_{3}$ (R = Li, Na and K) and $90Li_{2}B_{4}O_{7} + (10-x)PbO + xFe_{2}O_{3}$ (x = 0.5, 1, 3, 4, 5, 7
and 9 mol%) have been investigated by means of electron paramagnetic resonance (EPR) and optical absorption techniques. The EPR spectra exhibit three resonance signals at g=6.0, 4.2 and 2.0. The resonances at g=6.0 and 4.2 are attributed to $Fe^{3+}$ ions in rhombic and axial
symmetry sites, respectively. The g=2.0 resonance signal is due to two or more $Fe^{3+}$ ions coupled together with dipolar interaction. The EPR spectra of 1 mol% of $Fe_{2}O_{3}$ doped in lithium lead tetraborate glass samples have been studied at different temperatures (123-433 K).
The intensity of g=4.2 resonance signal decreases and the intensity of g=2.0 resonance signal increases with the increase of temperature. The line widths are found to be independent of temperature. The EPR spectra exhibit a marked concentration dependence on iron content. A
decrease in intensity for the resonance signal at g=4.2 with increase in iron content for more than 4 mol% has been observed in lithium lead tetraborate glass samples and this has been attributed to the formation of $Fe^{3+}$ ion clusters in the glass samples. The paramagnetic susceptibility (chi) is calculated from the EPR data at various temperatures and the Curie constant (C) has been evaluated from 1/chi versus T graph. The optical absorption spectrum of $Fe^{3+}$ ions in lithium lead tetraborate glasses exhibits three bands characteristic of $Fe^{3+}$ ions in an octahedral symmetry. The crystal field parameter Dq and the Racah interelectronic repulsion parameters B and C have also been evaluated. The value of
interelectronic repulsion parameter B (825 $cm^{-1}$ obtained in the present work suggests that the bonding is moderately covalent.
and 9 mol%) have been investigated by means of electron paramagnetic resonance (EPR) and optical absorption techniques. The EPR spectra exhibit three resonance signals at g=6.0, 4.2 and 2.0. The resonances at g=6.0 and 4.2 are attributed to $Fe^{3+}$ ions in rhombic and axial
symmetry sites, respectively. The g=2.0 resonance signal is due to two or more $Fe^{3+}$ ions coupled together with dipolar interaction. The EPR spectra of 1 mol% of $Fe_{2}O_{3}$ doped in lithium lead tetraborate glass samples have been studied at different temperatures (123-433 K).
The intensity of g=4.2 resonance signal decreases and the intensity of g=2.0 resonance signal increases with the increase of temperature. The line widths are found to be independent of temperature. The EPR spectra exhibit a marked concentration dependence on iron content. A
decrease in intensity for the resonance signal at g=4.2 with increase in iron content for more than 4 mol% has been observed in lithium lead tetraborate glass samples and this has been attributed to the formation of $Fe^{3+}$ ion clusters in the glass samples. The paramagnetic susceptibility (chi) is calculated from the EPR data at various temperatures and the Curie constant (C) has been evaluated from 1/chi versus T graph. The optical absorption spectrum of $Fe^{3+}$ ions in lithium lead tetraborate glasses exhibits three bands characteristic of $Fe^{3+}$ ions in an octahedral symmetry. The crystal field parameter Dq and the Racah interelectronic repulsion parameters B and C have also been evaluated. The value of
interelectronic repulsion parameter B (825 $cm^{-1}$ obtained in the present work suggests that the bonding is moderately covalent.
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pdf http://eprints.iisc.ernet.in/archive/00003654/01/A158.pdf
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