Dielectric properties and scaling behavior of lithium tungsten phosphate glasses
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In the present study a series of ternary (30 Li2O, (70-x) P2O5, xWO3) glasses were prepared and their dielectric properties and ac conductivity were investigated. The measurements have been taken in the frequency range from 100 Hz to 100 kHz and over the temperature range from 296 K to 578 K. The temperature dependence of ac conductivity can be adequately explained by considering the contributions from mixed ionic and electronic mechanisms. In the studied glasses it is found that the ac conductivity increases with increasing frequency. By investigating the relation between temperature and the frequency exponent “s” of the power law σac = Aωs, it is found that the Correlated Barrier Hopping model (CBH) is appropriate for describing the conduction mechanism in the samples. In an attempt to investigate the universality of ac conductivity in these glasses, it is found that the data obtained follow Rolling scaling model. When considering the dielectric properties, it is found that the M″vs. M′ plots give master Cole-Cole curves at all temperatures. These results can be considered as an indication of the presence of space charge or accumulation of charges in some regions inside the samples. The relation between M″/ Mmax″ and f/f p represent a master plot at different temperatures. These scaling suggest the existence of a distribution of potential wells, in which the carriers are trapped.
KeywordsLithium tungsten phosphate glasses Dielectric properties ac conductivity and scaling models
The authors wish to thank Prof. M.K.El-Nimer , physics Department, Faculty of Science, Tanta University for allowing us to carry out the experimental work ac measurements electrical conductivity and for fruitful discussions.
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