Microwave conductivity of NiO at high temperatures

The microwave conductivity σ(ω) at an angular frequency ω of 3.03 × 1011 rad s−1 and the dc conductivity σ(0) of NiO single crystals are measured in the temperature range from 803 to 1673 K at an oxygen pressure of 10−3 Torr. The frequency dependence of σ(ω) is different in the temperature range above and below 1423 K. An interpretation of the results is given with some discussion.