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Mixed Alkali Effect in $Li_{2}O -Na_{2}O-B_{2}O_{3}$ Glasses Containing CuO-An EPR and Optical Study

UNSPECIFIED (2005) Mixed Alkali Effect in $Li_{2}O -Na_{2}O-B_{2}O_{3}$ Glasses Containing CuO-An EPR and Optical Study. In: 50th DAE Solid State Physics Symposium, Dec. 5 - 9, 2005, Bhabha Atomic Research Centre, Mumbai.


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The "mixed alkali effect" is one of the classical anomalies of glass science. We report here an interesting phenomenon "Mixed Alkali Effect" observed for a series of $Cu^{2+}$ ions doped $xLi_{2}O-(30-x)Na_{2}O-70B_{2}O_{3}$ (5 \leq x \leq 25) glasses, investigated by EPR and optical absorption techniques. The EPR spectra of all the investigated samples exhibit resonance signals characteristic of $Cu^{2+}$ ions in octahedral sites with tetragonal distortion. It is found that the spin-Hamiltonian parameters do not vary much with x. However, the number of spins participating in resonance (N) and the paramagnetic susceptibility (\chi) exhibits the mixed alkali effect. The N is also measured as a function of temperature and the activation energy is evaluated. It is observed that the temperature dependence of paramagnetic susceptibility (\chi) obeys Curie-Weiss law. The optical absorption spectra exhibit a strong band corresponding to the transition $(^{2}B_{1g} -> ^{2}B_{2g})$ centered at 13280 $cm^{-1}$. By correlating the EPR and optical absorption data, the molecular orbital coefficients $\alpha^{2}$ and $\beta^{2}_{2}$ are evaluated. It is interesting to observe that the optical band gap and Urbach energies show the MAE.

Item Type: Conference Proceedings
Keywords: Mixed Alkali Effect;Glasses;CuO;EPR;Optical
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 10 Oct 2006
Last Modified: 19 Sep 2010 04:22
URI: http://eprints.iisc.ernet.in/id/eprint/4421

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