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

TL;DR

This study investigates how inversion and cation disordering in magnesium gallium spinel influence its thermal diffusivity at high temperatures, revealing a new heat transport mechanism linked to cation site changes.

Contribution

It demonstrates that cation site occupancy changes significantly affect thermal diffusivity, introducing a novel aspect of heat transport in spinel materials.

Findings

Thermal diffusivity increases above 950°C, deviating from typical behavior.

Small change in inversion parameter x with annealing temperature.

Cation site changes contribute to heat transport at high temperatures.

Abstract

Measurements of thermal diffusivity \k{appa} (using laser flash analysis) for temperatures from 100 {\deg}C to 1200 {\deg}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 {\deg}C (x = 0.838) and 1200 {\deg}C (x = 0.834). Thermal diffusivity revealed a significant rise of \k{appa} for temperatures higher than 950 {\deg}C, deviating from the typical 1/T drop of \k{appa}. An additional systematic rise of \k{appa} with time is observed for temperatures between 950 {\deg}C and 1100 {\deg}C. A connection between cation disordering processes typical for spinels at elevated temperatures and the observed deviation of \k{appa} is proposed: Data indicate that cations changing their occupancy site at equilibration processes contribute significantly to \k{appa} and therefore represent a new type of heat transport.