In-situlaser synthesis of Nd–Al–O coatings: the role of sublattice cations in eutectic formation

Abstract

Neodymium aluminate coatings have been preparedin-situby the laser zone melting (LZM) method, using a CO2SLAB-type laser emitting at 10.6 µm. Polycrystalline Al2O3commercial plates have been used as substrates, and coatings were prepared from the corresponding mixtures of powdered neodymium and aluminium oxides as starting materials. Microstructure, studied by SEM and phase composition, studied by XRD, proved thein-situformation of a NdAlO3/NdAl11O18eutectic. As a result, a well integrated composite coating was formed. Nanoindentation tests are consistent with excellent integration between coating and substrate. Structural similarities between the eutectic components within the coating, as well as between these and the substrate, are consistent with the crystallographic concepts proposed by Vegas (Ramos-Gallardo & Vegas, 1997), where cation sub-arrays play an important role governing metal oxide structures. These structure sublattices are suggested as the driving force behind eutectic oxide formation.