Electronic Conductivity of Single Crystalline Magnesium Oxide

The electronic conductivity of MgO was determined by measuring the dc conductivity and ionic transference number as a function of temperature (1200° to 1600°C), oxygen pressure (10 −1 to 10 −13 MPa), and trivalent solute concentration (65 to 1500 ppm) using samples doped with Al, Fe, or Sc so that only one dopant controlled the defect structure. The electronic conductivity showed a p ‐ to n ‐type transition with decreasing oxygen pressure, consistent with a defect structure in which the concentrations of the electronic species are negligible with respect to those of the ionic defects, so that MgO is a fully compensated semiconductor. From the temperature dependence of the electronic conductivity minima, a thermal band gap of 650±50 kj/mol (6.8±0.5 eV/electron) and electron and hole mobilities of 24 and 7 cm 2 /V·s were determined at 1400°C. From these results, the defect‐reaction equilibrium constants were determined.