Dielectric dispersion in lithium–bismuth-borate glasses

Glasses with compositions xBi2O3–(75–x) B2O3–25Li2O with, x = 0, 5, 20, 25,30,35,40 mol % have been prepared using the normal melt quenching technique. The dielectric constant (έ) dielectric loss tangent tan δ, electric modulus behaviour was studied as a function of temperature in the frequency range 0.1–100 kHz. The detailed analysis of the results showed that the dielectric dispersion consists of both dipolar and interfacial polarization. Also the activation energy of the dielectric relaxation process from the electric modulus measurements was calcaulated. Measurements of the ac conductivity as a function of frequency at different temperatures indicated that the correlated barrier hopping (CBH) model is the most suitable mechanism for the ac conduction behaviour. The ac parameters, such as hopping distance (R, Rmin), polaron binding energy (UM) and Columbic barrier height (Uh) were calculated.