Kesavulu, C R and Chakradhar, R P S and Jayasankar, C K and Rao, J Lakshmana (2010) EPR, optical, photoluminescence studies of Cr(3+) ions in Li(2)O-Cs(2)O-B(2)O(3) glasses - An evidence of mixed alkali effect. Journal of Molecular Structure, 975 (1-3). pp. 93-99. ISSN 0022-2860

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Abstract

This paper reports the results on mixed alkali effect (MAE) in xLi(2)O-(30-x)Cs(2)O-69.25B(2)O(3) (5 <= x <= 25) glasses doped with 0.75 mol% of Cr(3+) ions studied by Electron Paramagnetic Resonance (EPR), optical absorption and luminescence techniques. The EPR spectra exhibit two resonance signals with effective g values at g approximate to 4.82 and g approximate to 1.99. These two resonance signals are attributed to isolated Cr(3+) ions and exchange coupled Cr(3+) pairs respectively. In addition to this, two more resonance signals with effective g values at g approximate to 4.12 and g approximate to 1.97 are also observed. The resonance signal at g approximate to 4.12 is due to Fe(3+) ions impurity and the resonance signal at g approximate to 1.97 is due to Cr(5+). ions. The population of spin levels (N) for the resonance signal at g approximate to 1.99 has been calculated at room temperature. It is interesting to observe that N exhibits a non-linear behavior with change in composition showing the mixed alkali effect. The magnetic susceptibility (chi) was calculated from the EPR data at various temperatures. The exchange coupling constant J between Cr(3+) ions is calculated from relative intensities of g approximate to 1.99 resonance line. The optical absorption spectrum exhibits three bands characteristic of Cr(3+) ions in octahedral symmetry. From the optical absorption spectral data, the crystal field (Dq) and Racah parameters (B and C) have been evaluated. From ultraviolet absorption edges, the optical band gap and Urbach energies have been calculated. The luminescence spectrum exhibits a red emission peak observed at 640 nm which is assigned to a transition (2)E(g) —> (4)A(2g) of Cr(3+) ions. (C) 2010 Elsevier B.V. All rights reserved.

Item Type:	Article
Uncontrolled Keywords:	Electron Paramagnetic Resonance (EPR); Optical; Photoluminescence; Cr3+
Subjects:	Glass
Divisions:	UNSPECIFIED
Depositing User:	Bidhan Chaudhuri
Date Deposited:	13 Feb 2012 10:37
Last Modified:	28 Mar 2016 16:59
URI:	http://cgcri.csircentral.net/id/eprint/800

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