Question: what is the difference between alpha and gamma alumina?
Answer: [I]α- Alumina has a trigonal structure (R-3c) with ABAB stacking of oxygen planes along the c-direction with Al (III) in 2/3 of the octahedral interstitial positions. γ – Alumina is cubic with space group Fd-3m and an fcc . . . ABCABC. . . stacking of oxygen.