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Light Scattering in Ionic Conductor Li2B4O7 Crystals in the High-Temperature Region

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Author(s): V.N. Moiseyenko | M.P. Dergachov | Ya.V. Burak

Journal: Ukrainian Journal of Physical Optics
ISSN 1609-1833

Volume: 6;
Issue: 2;
Start page: 45;
Date: 2005;
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Keywords: light scattering | ionic conductivity | phase transition

ABSTRACT
Isofrequency temperature dependences of Rayleigh and hyper-Rayleigh scattering intensities have been measured in isotopically substituted Li2B4O7 crystals within a wide temperature range (300–1000 K). The dependences contain two anomalies in the vicinities of 520 and 800 K. The first anomaly is associated with hopping of lithium ions between two non-equivalent positions, with the activation energy of about 0.23 eV. The second one results from the first-order order-disorder phase transition due to the melting of lithium sublattice. The temperature dependence of the relaxation time obtained by analysing quasi-elastic light scattering spectra is satisfactorily described, using the theoretical relation typical for such the phase transitions, with the relevant parameters Tc = 790 K and D = 0.95.
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