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Kinetics of Phase Transformation in fcc-(Al0.32Cr0.68)2O3 Thin Films
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Thermal stability of fcc-(Al0.32Cr0.68)2O3 thin film is investigated by ex-situ annealing of films in the temperature range of 500-1100 °C and annealing times of 2-10 h. X-ray diffraction indicates that the phase transformation from fcc to corundum crystal structure starts at 925 °C and completes at 1000 °C. This is further confirmed by high resolution transmission electron microscopy and selected area electron diffraction. The kinetics of phase transformation is analyzed by Johnson-Avrami-Mehl model. The phase transformation from fcc to corundum in (Al0.32Cr0.68)2O3 thin films is a two-stage thermally activated process. The first stage is phase transformation and has the apparent activation energy of 213±162 kJ/mol (0.44±0.34 eV/atom). This is followed by a second stage with a larger apparent activation energy of 945±27 kJ/mol (1.96±0.06 eV/atom). This is likely associated with the grain growth of a-phase upon completion of the phase transformation.

National Category
Natural Sciences
URN: urn:nbn:se:liu:diva-65699OAI: diva2:398419
Available from: 2011-02-17 Created: 2011-02-17 Last updated: 2011-12-05Bibliographically approved
In thesis
1. Deposition and Phase Transformations of Ternary Al-Cr-O Thin Films
Open this publication in new window or tab >>Deposition and Phase Transformations of Ternary Al-Cr-O Thin Films
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerns the ternary Al-Cr-O system. (Al1-xCrx)2O3 solid solution thin films with 0.6<x<0.7 were deposited on Si(001) substrates at temperatures of 400-500 °C by reactive radio frequency magnetron sputtering from metallic targets of Al and Cr in a flow controlled Ar / O2 gas mixture. As-deposited and annealed (Al1-xCrx)2O3 thin films were analyzed by x-ray diffraction, elastic recoil detection analysis, scanning electron microscopy, transmission electron microscopy, and nanoindentation. (Al1-xCrx)2O3 showed to have face centered cubic structure with lattice parameter of 4.04 Å, which is in contrast to the typical corundum structure reported for these films. The as-deposited films exhibited hardness of ~ 26 GPa and elastic modulus of 220-235 GPa. Phase transformation from cubic to corundum (Al0.32Cr0.68)2O3 starts at 925 °C. Annealing at 1000 °C resulted in complete phase transformation, while no precipitates of alumina and chromia were observed. Studies on kinetics of phase transformation showed a two-step thermally activated process; phase transformation and grain growth with the apparent activation energies 213±162 and 945±27 kJ/mol, respectively.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 29 p.
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1474
Thin Films, Hard Coatings
National Category
Other Physics Topics
urn:nbn:se:liu:diva-65700 (URN)LIU-TEK-LIC-2011:13 (Local ID)978-91-7393-210-3 (ISBN)LIU-TEK-LIC-2011:13 (Archive number)LIU-TEK-LIC-2011:13 (OAI)
2011-04-15, Hörsal Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Available from: 2011-12-05 Created: 2011-02-17 Last updated: 2016-08-31Bibliographically approved

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