Electrical Conduction Properties of Liquid Vanadates. III. The System V2O5–Na2O–Fe2O3
The liquid ferric vanadates exhibited n-type semiconduction properties at oxygen partial pressures greater than 0.1 atm. For ferric oxide concentrations less than 16 mol%, the activation energy of conduction was less than the activation energy associated with liquid vanadium pentoxide, but at greater ferric oxide concentrations, the activation energy increased to values greater than that associated with liquid vanadium pentoxide. The negative oxygen partial pressure coefficients of conduction were found to decrease with increasing ferric oxide concentration. The addition of sodium oxide to the liquid ferric vanadates decreased the activation energies of conduction. The electrical conductivities of these sodium ferric vanadates were found to be independent of oxygen partial pressure.The electrical conduction mechanism of the ferric vanadates was considered to involve the movement of delocalized electrons or polarons between V4+ and V5+ centers at low ferric oxide concentrations and the additional movement of delocalized electrons between Fe2+ and Fe3+ centers for ferric oxide concentrations greater than 16 mol%. The addition of sodium oxide to the liquid ferric vanadates apparently changed the electrical conduction mechanism from semiconduction to ionic conduction. Sodium and oxygen ions are probably the charge-carrying species in these ionic melts.