On the influence of inversion on thermal properties of magnesium gallium spinel.

Measurements of thermal diffusivity ? (using laser flash analysis) for temperatures from 100 °C to 1200 °C and of the inversion parameter x (using X-ray analysis) for the single crystal spinel MgGa₂O₄ have been performed. X-ray analysis showed a small change in x for samples annealed at 800 °C (x = 0.838) and 1200 °C (x = 0.834). Thermal diffusivity revealed a significant rise of ? for temperatures higher than 950 °C, deviating from the typical 1/T drop of ?. An additional systematic rise of ? with time is observed for temperatures between 950 °C and 1100 °C. A connection between cation disordering processes typical for spinels at elevated temperatures and the observed deviation of ? is proposed: Data indicate that cations changing their occupancy site at equilibration processes contribute significantly to ? and therefore represent a new type of heat transport. [ABSTRACT FROM AUTHOR]