Effect of Processing Conditions on Thermal Conduction in Alumina

Abstract

Thermal conductivity versus temperature data, in the temperature range 77 to 500 K, is presented for a series of seven alpha alumina samples sintered at temperatures varying from 1273 K to 1873 K. Peaks in thermal conductivity are observed for the five samples sintered at < 1773 K. A shift in the magnitude and location of the peaks and an increase in the overall magnitude of thermal conductivity over the entire temperature range are observed with increasing sintering temperature. It is concluded that the temperature dependence of thermal conductivity of these materials is determined by two contributing factors: a) An increase in density as the sintering temperature is increased which leads to the removal of internal thermal barriers and an increase in the effective cross sectional areas of the samples b) An increase in the phonon mean free path for samples sintered at higher temperatures. This may be due in part to an increase in the intrinsic thermal conductivity of the grains.