The effects of Cr2O3 and Fe2O3 additions on the thermal conductivity of Al2O3

Thermal conductivity data for a series of Al2O3, Al2O3-Cr2O3, Al2O3-Fe2O3, and Al2O3-Cr2O3-Fe2O3 samples are reported. The results, which span the temperature range 300–360 K, show that grain size has an important effect on the thermal conductivity of Al2O3, and this effect is larger than would be anticipated from standard theories. Results for seven Al2O3-based solid solutions were examined in terms of a Callaway formula, and it was found that the point defect relaxation times were principally dependent on solute content and the mass difference between the solute and solvent. The data support a theory that suggests that a heavy atom in a light matrix scatters less effectively than a light atom in a heavy matrix. The data do not show that isolated point defects are more effective phonon scatterers than point defects in a concentrated solution.