Preparation,electrical and photoelectrochemical properties of magnesium doped iron oxide sintered discs

Sintered discs of magnesium substituted iron oxides have been prepared by gel routes or classical solid state reaction techniques and their crystallographic, electrical, and photoelectrochemical properties examined. The discs, sintered between 1200 and 1400°C for 20 hours, contain both α-Fe₂O₃ and a spinel phase. The electrical properties of the discs have been correlated with spinel concentration, the electrical resistivity decreasing with increasing spinel content. The materials were found to be consistently n-type by Seebeck voltage measurements. Photoelectrochemical measurements in aqueous solution showed however that the sintered disc electrodes exhibit photocathodic currents that are characteristic of p-type semiconductors. Evidence is presented which suggests that inhomogeneities in the near surface region of the discs are responsible for the observed photoelectrochemical properties.