Abstract
The dependence of the thermoelectric power and the electrical conductivity of chromium(III)oxide on the oxygen partial pressure was studied in the temperature range from 1000 to 1800 K. At low oxygen partial pressures n‐type behavior is observed, while the material is p‐type at high oxygen partial pressures. Both n‐ and p‐type material can be obtained at temperatures as high as 1800 K, which means that up to this temperature chromium(III)oxide is not an intrinsic electronic conductor. The transition from n‐ to p‐type is relatively fast, and proceeds at a considerable rate at temperatures above 1200 K. However a shift from p‐ to n‐type does not take place below 1770 K. Two models for this phenomenon are presented. The present results provide evidence for a defect model for 
with 
as predominating point defects at low oxygen partial pressures and V‴Cr at high oxygen partial pressures. Furthermore, it is concluded that the bandgap is larger than 3.6 eV. The transport properties of chromia scales during high temperature oxidation are discussed in view of these new data on the defect structure of chromium(III)oxide.