Electrical conduction of MgO doped with Cr at high temperatures in oxidizing atmosphere

The electrical conductivities of MgO crystals doped with Cr are measured at high temperatures up to 2900 K in air, by using the de method (1300 to 1820 K) and microwave ellipsometry (2600 to 2900 K). Interpretation of the results obtained below 1820 K is made by a cation vacancy complex model; ionic conduction by cations is prominent below 1540 K, while electronic conduction by holes is prominent above 1540 K. From the results obtained by microwave ellipsometry above 2600 K, an intrinsic thermal energy gap of MgO is estimated to (7.9 ± 0.7) eV which is in a good agreement with the optical energy gap.