First-principles characterization of a heteroceramic interface: ${\mathrm{ZrO}}_2\mathrm{}\left(001\right)\mathrm{}$ deposited on an $\alpha -{\mathrm{Al}}_2{\mathrm{O}}_3\left(11\mathrm{}¯02\right)$ 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 ${\mathrm{ZrO}}_2\mathrm{}\left(001\right)/\alpha -{\mathrm{Al}}_2{\mathrm{O}}_3\left(11\mathrm{}¯02\right)$ interface as well as of the free $\alpha -{\mathrm{Al}}_2{\mathrm{O}}_3\left(11\mathrm{}¯02\right)$ and ${\mathrm{ZrO}}_2\mathrm{}\left(001\right)\mathrm{}$ 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 ${\mathrm{ZrO}}_2\mathrm{}\left(001\right)\mathrm{}$ 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 ${\mathrm{ZrO}}_2\mathrm{}\left(001\right)/\alpha -{\mathrm{Al}}_2{\mathrm{O}}_3\left(11\mathrm{}¯02\right)$ interface has a rather epitaxial character, due to a low lattice mismatch of $\sim 4\%.$ The impact of such weak interactions on ceramic coating stability is discussed.