Structural investigation and dc conductivity of Bi2O3–B2O3 glasses

Abstract

The structure of xBi2O3∙(100–x)B2O3 with (30 ≤ x ≤ 65 mol%) glasses was investigated by FTIR, XRD, TEM, SEM and dc conductivity. The factor of four coordinated boron atoms N4 increases up to 50 mol% Bi2O3 then decreases for further increase in Bi2O3 content. FTIR analyses indicate that Bi2O3 heads for creating a matrix of its own rather than modifying the borate matrix and this behavior gradually increases with increasing its concentration in the matrix. There is a linear increase in both experimental density and molar volume values with replacing B2O3 by Bi2O3, moreover a strong correlation between the computed and experimental density and molar volume values could be noticed. XRD patterns confirm that no sharp peaks for untreated samples whereas Bi2O3 crystalline phase appears for heat treated samples. TEM and SEM show the presence of some small phases with different sizes formed of clusters, these phases increase in size and became predominant with heat treatment. The conductivity increases while the activation energy seems to be constant. This rare behavior is interpreted in the light of forming Bi2O3 former matrix.