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.

Research highlights▶ We have studied the effects of temperature and duration on the formation mechanism and kinetics of Mg-Al spinel layer. ▶ A combined investigation on the difference of the growth of the spinel layer between the polycrystalline and monocrystalline alumina substrates also have been investigated. ▶ The growth of formed Mg-Al spinel layer under 1300 °C and 1600 °C is discussed, as well as the thickness and orientation of the formed Mg-Al spinel.