Synthesis and study of electrical properties of Li2O modified P2O5-ZnO-Na2O glasses

Document Type : Original Article

Authors

1 Physics Department, Modern Academy for Engineering and Technology in Maadi, Cairo, Egypt

2 Physics Department, Faculty of Science, Al-Azhar University, Cairo, Egypt

3 National Research Center, Dokki, Cairo, Egypt

4 Physics Department, Faculty of Women, Ain Shams University, Cairo, Egypt

Abstract

The transparent glasses of composition 40P2O5-20ZnO-(40-x)Na2O-xLi2O have been prepared using conventional melt quenching technique (where 0 ≤ x ≤ 25 Li2O mol. %). The amorphous nature of the prepared glass samples is confirmed by x-ray powder diffraction (XRD). By increasing the Li2O content, the density and oxygen packing density increase while the molar volume decreases which indicates that the structure is more compact. The differential thermal analysis (DTA) studies showes that 15 mol.% Li2O glass sample has the highest thermal stability and the glass transition temperature (Tg) decreases as the content of Li2O increases till 25 mol.% Li2O . The ac and dc electrical conductivities and dielectric constants of the prepared glass samples have been investigated. It is found that the          dc conductivity increases with the concentration of Li2O mol.% and the temperature dependence of the dc conductivity at low temperature (303 – 383 K) and at high temperature (403 – 473 K) obey the Arrhenius law. The activation energies ΔEdc1 (at high temperatures) and ΔEdc2 (at low temperatures) were determined. The values of σdc can be obtained also from the impedance study at different temperatures and different concentrations using Cole-Cole plot. To determine the conduction mechanism, the ac conductivity and its frequency exponent (s) have been analyzed by correlated barrier hoping model (CBH). It is found that s has values between 0.89-0.996; consequently. The correlated barrier hopping (CBH) seems to be the most interesting model related to the obtained results. Real and imaginary parts of dielectric constant (ε' and ε'') have been found to decrease with increasing frequency and temperature and this result would be discussed by means of dielectric polarization mechanism of material. The maximum value of the maximum barrier height Wm obtained from Guitini equation was found to increase with increasing of Li2O mol. %.

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