Influence of the temperature and duration of the annealing on the lattice structure and growth of the Mg–Al spinel layer

In this paper, MgO film is successfully grown on polycrystalline and monocrystalline alumina substrates using sol–gel method, and polycrystalline and monocrystalline Mg–Al spinels are fabricated by solid state reaction, respectively. The influence of annealing temperature and time on the lattice structure and growth of the formed Mg–Al spinel layer has been investigated. It is indicated that the annealing temperature and time on the as-synthesized polycrystalline Mg–Al spinel has more significant influence than that of single crystal Mg–Al spinel. The thickness of the Mg–Al spinel layer increases with the annealing temperature, both for polycrystalline and for monocrystalline alumina substrates. And the significantly intercrystalline diffusion of Mg2+ ions and Al3+ ions results in a quicker growth velocity of the Mg–Al spinel layer than that of intracrystalline diffusion.