| AVS 60th International Symposium and Exhibition | |
| Advanced Surface Engineering | Thursday Sessions |
| Session SE+NS+TF-ThA |
| Session: | Nanostructured Thin Films and Coatings |
| Presenter: | J.M. Schneider, RWTH Aachen University, Germany |
| Authors: | F. Nahif, RWTH Aachen University, Germany D. Music, RWTH Aachen University, Germany S. Mráz, RWTH Aachen University, Germany H. Bolvardi, RWTH Aachen University, Germany L. Conrads, RWTH Aachen University, Germany J.M. Schneider, RWTH Aachen University, Germany |
| Correspondent: | Click to Email |
The effect of Si additives on the phase transformation sequence and phase formation temperatures was investigated for filtered cathodic arc deposited Al2O3 thin films.
The here obtained XRD data suggest that by addition of Si the transformation of γ- to δ- and θ-Al2O3 is restrained by 100°C extending the thermal stability range of the δ- and θ-phase by ≥ 200°C with respect to the unalloyed Al2O3 thin film. The formation of α-Al2O3 is restrained by 200°C upon addition of Si. Furthermore, the formation of orthorhombic mullite is observed at ≥ 1300°C for the Si alloyed samples, while single phase α-Al2O3 is obtained for the unalloyed films at 1100°C.
According to the experimentally observed stabilization of the metastable γ- to δ- and θ-Al2O3 phases and the restrained α-Al2O3 phase formation upon Si addition the presence of amorphous SiO2 at the grain boundaries, which may impede mass transport and hence crystalline growth, appears to be the cause of the here reported stabilization. Inconsistency of the Si bonding data obtained by XPS with the notion of a solid solution of Si in the alumina lattice suggests that this cannot serve as an explanation for the stability enhancement.