Effects of microstructural evolution on the thermal conductivity of α–Al₂O₃ prepared from nano-size γ–Al₂O₃ powder

The thermal diffusivities (D) of porous α–Al₂O₃ specimens prepared from nano-size γ–Al₂O₃ powder and from conventional submicrometer-size alumina powders were measured at room temperature, and the thermal conductivity (κ) was calculated from D. Plots of κ versus the volume fraction of porosity (P) showed that the data from both sets of samples followed similar linear curves. Similarly, data of Vickers hardness versus P obtained from the same specimens also followed a single linear curve. The good correlation of thermal diffusivity with P suggests that grain boundaries have a lesser effect on thermal transport than porosity.