Activation energy of fcc-corundum phase transformation in (Al1-xCrx)2O3 Thin Films
2011 (English)Conference paper, Presentation (Other academic)
Face centered cubic (Al1-xCrx)2O3 solid solution films, with x in the range 0.60<x<0.70, have been deposited using dual reactive RF magnetron sputtering from Al and Cr targets in mixed Ar/O2 discharge at a substrate temperature of 500 °C. The films have a strong <100> preferred orientation. The unit cell parameter is 4.04 Å determined by x-ray diffraction and high resolution transmission electron microscopy techniques. The (Al1-xCrx)2O3 films are suggested to have a non-stoichiometric NaCl structure with 33% vacancy occupancy on Al/Cr sites. Nanoindentation shows that the films exhibit hardness values up to 26 GPa and reduced modulus of 220-235 GPa. In the present work, in-situ annealing studies were performed on as-deposited samples for a series of temperatures up to 1000 °C and annealing time of 8 h. The fcc structure remains intact up to 700 °C. A gradual phase transformation from fcc to corundum at 1000 °C is observed, where annealing for 1-3 h yields a partial transformation and annealing for > 4 h results in complete transformation to a-(Al1-xCrx)2O3. There is no indication of any phase separation into a-Cr2O3 and Al2O3.
Place, publisher, year, edition, pages
National CategoryManufacturing, Surface and Joining Technology Physical Sciences
IdentifiersURN: urn:nbn:se:liu:diva-84379OAI: oai:DiVA.org:liu-84379DiVA: diva2:558846
15th International Conference on Thin Films (ICTF-15), 8-11 November 2011, Kyoto, Japan