Thermal and Thermodynamic Properties

1.3 Density and Thermal Expansion

The density of alpha alumina at 25°C is 3.96 g cm-3, which gives a specific volume of 25.8 cm3 mol-1 or 0.0438 nm3 per Al2O3 molecule. Densities of other aluminas are given in Table 12.

The coefficient of thermal expansion a of alumina at different temperatures is given in Table 13. Often an average value of a is given over a range of temperatures, but the slope of a length vs. temperature plot at different temperatures is a more accu­rate way of describing a.