Atomic structures of faceted low-energy Pd/Al2O3 interfaces

Abstract

Recently, it has been demonstrated that alpha alumina fibers having the stable trigonal structure can be grown in Pd by internal oxidation. The alumina fibers are oriented with respect to Pd and exhibit strong faceting. In this paper, we present HREM results on the atomic structures of the faceted interfaces.Oxidation experiments were done in air at 1000 °C for 48 hrs on a Pd-10.8 at.% Al alloy. Selected samples were subsequently annealed at 1000 °C for 0.5 hrs in an Al vapor. All HREM observations were done using a Topcon-002B high resolution microscope. For image analysis, the interfaces were modeled using EPITAX and multislice image simulations were performed using EMS programs.The alumina fibers grown by internal oxidation, grow along the <110>Pd oxidation front direction. The orientation relationship between Al2O3 fibers and Pd is not unique, however, most fibers are faceted with primary low energy interfaces between Pd and Al2O3 corresponding to (110)//(0001), (111)//(0001) and (111)//(11-20).