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ICMCTF - 2015
Christian Koller (C.M. Koller)
"Role of Droplets in the Phase Formation of Arc Evaporated (Al0.70Cr0.25Fe0.05)2O3 Coatings"
Christian Koller ; Vienna University of Technology, Austria
Jürgen Ramm ; Oerlikon Balzers Coating AG, Liechtenstein
Szilárd Kolozsvári ; Plansee Composite Materials GmbH, Germany
Jörg Paulitsch ; Oerlikon Balzers Coating Austria GmbH, Austria
Paul Mayrhofer ; Vienna University of Technology, Austria
By alloying small amounts of Fe to (Al0.7Cr0.3)2O3 cathodic arc evaporated thin films a significant increase in hexagonal phase fractions can be attained. However, the reasons for the enhanced occurrence of hexagonal crystallitesis not yet satisfactorily determined. Therefore, the focus of the present work is set on incorporated macroparticles in (Al0.7Cr0.3Fe0.05)2O3 coatings and a potential correlation with the growth of distinct V-shaped hexagonal crystallites.
Detailed transmission electron microscopy studies give strong indication for film growth of an α-phased solid solution (Al,Cr,Fe)2O3—at least partially—triggered by smaller spherical droplets. Local analyses of the chemical composition of these particles reveal an enrichment of Cr and—in particular—Fe. Contrarily, flat-shaped Al-rich particles indicate re-nucleation of cubic film growth, independent on the phase constitution on which the droplet is incorporated. Additional studies on other—predominant cubic phased—coatings demonstrate that respective effect is also present, albeit less frequent.
According to present results we suggest, that the addition of Fe to powder metallurgically produced Al0.7Cr0.3 targets for arc evaporation processes in oxygen atmosphere significantly contributes to enhanced hexagonal crystal growth due to partial epitaxy on small Fe-rich particles.

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