First-principles characterization of a heteroceramic interface: ZrO₂(001) deposited on an α-Al₂O₃(11̄02) substrate

We have studied an alumina/zirconia interface using the all-electron projector augmented wave formalism within density functional theory. We present the electronic, structural, and energetic properties of the ZrO₂(001)/α-Al₂O₃(11̄02) interface as well as of the free α-Al₂O₃(11̄02) and ZrO₂(001) surfaces. We find that the generalized gradient correction significantly lowers the oxide surface energies, compared to values obtained by the local density approximation. The monoclinic-tetragonal transition in ZrO₂(001) thin films is discussed as well as strain effects involved in the interface formation. The stoichiometric alumina/zirconia interface is found to be weakly bonded, regardless of the film thickness, and the ZrO₂(001)/α-Al₂O₃(11̄02) interface has a rather epitaxial character, due to a low lattice mismatch of ∼4%. The impact of such weak interactions on ceramic coating stability is discussed.