The  reaction between [Al] and [O] can be expressed by  2[Al] + 3[O] = Al2O3(s) (5)  ∆GѲ = −1218799 + 394.13 T (6)  Considering fAl = fO = 1, and when T = 1873 K, there are  %Al %O 1.5 = 2.00 × 10−7 (7)