ELECTRICAL, OPTICAL AND PHOTOCONDUCTING PROPERTIES OF FE2-XCRXO3 (0LESS THAN OR EQUAL TOXLESS THAN OR EQUAL TO0.47)

A study has been made of the electrical, optical and photoconducting properties of pure and reduced single crystals of composition Fe2-xCrxO3 where 0 ≤ x ≤ 0.47. It has been found that pure α-Fe2O3 is not a photoconductor. When defect-free crystals of α-Fe2O3 are reduced a surface layer of Fe3O4 is formed and the crystals exhibit photoconductivity. Removal of this layer resulted in the disappearance of photocurrents and an increase in the sample resistivity. A necessary condition for the observation of photocurrents in n-type Fe2O3 is that some Fe3O4 be present. In addition, it has been found that the substitution of chromium for iron in α-Fe2O3 results in a monotonically decreasing optical band gap as the chromium concentration, x, increases. © 1979.