Study of conduction mechanism in Fe2O3 doped Na2O·Bi2O3·B2O3 semiconducting glasses

Conduction mechanism in Fe2O3 doped Na2O·Bi2O3·B2O3 semiconducting glass system was studied in frequency range 10 Hz to 1 MHz and at temperatures between room temperature and 663 K. The total conductivity spectrum follows universal power law with frequency exponent ‘s’ value less than unity and lies in the range 0.51≤s≤0.78. These ranges of ‘s’ values indicate that the carrier transport is predominately due to hopping electrons between charged defects and show temperature dependence as predicted by correlated barrier hopping (CBH) model. The change in activation energy of dc conductivity with temperature reveals the change in conduction mode from small polaron hopping (SPH) at high temperatures (T>θD/2) to variable range hopping (VRH) at low temperatures (T<θD/2). The range of density of states at Fermi level N (EF)=7.25×1021–1.32×1021 eV−1 cm−3 at temperatures below θD/2 corresponds to localized states near Fermi level. The large values of activation energy W2 (0.067–0.155 eV) dominated the conduction may results in high range of temperature (T=503– 423 K) for variable-range hopping conduction in these glasses.