Borophosphate glasses of composition, (B₂O₃)_0.2 (P₂O₅)_0.8-x (V₂O₅)_x with x = 0.35, 0.40, 0.45, 0.50, 0.55 and 0.60 were synthesized. Room temperature density and the conductivity for the temperature range from 300 K to 650 K were measured. Density decreased up to 0.45 mole fractions of V₂O₅, increased for 0.5 mole fractions and decreased thereafter. By employing Mott’s SPH (Small Polaron Hopping) model, activation energy for conduction has been determined. Activation energy decreased with increasing V₂O₅ content up to 0.55 mole fractions and increased for further amounts of V₂O₅. Conductivity behaved in the opposite fashion to that of activation energy with V₂O₅ concentration. Increase in conductivity for V₂O₅ up to 0.55 mole fractions and decrease for higher concentrations may be attributed to mixed glass former (MGFE) effect occurring around 0.55 mole fractions of V₂O₅. Conductivity data that was not in agreement with Mott’s SPH model has been considered in the light of variable range hopping models of Mott and Greaves. Density of states at Fermi level from both the model fits have been determined and compared. Various polaron hopping related parameters were estimated. For the first time MGFE has been observed in V₂O₅ doped borophosphate glasses of present compositions.
Keywords: Borophosphate Glasses; Density; Conductivity; Polaron Hopping;