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  4. An experimental and theoretical study on the crystal structure and elastic properties of Ta 1-xOx coatings
 
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2019
Journal Article
Title

An experimental and theoretical study on the crystal structure and elastic properties of Ta 1-xOx coatings

Abstract
The production of Ta1-xOx coatings has attracted a lot of attention due to their wide variety of industrial applications. Nonetheless, to properly control the functional properties of these coatings, a good understanding of their structural properties must be achieved. Ta1-xOx phases have structural similarities since they are formed by the distortion of the body centered cubic (bcc) Ta structure and, therefore, a clear and unequivocal identification of the crystalline phases is not trivial. In this regard, this work proposes a theoretical and experimental study to understand the evolution of the structural and the elastic properties of Ta-based coatings. The coatings were deposited by magnetron sputtering as a function of oxygen content and characterized by EPMA (electron probe microanalysis), XRD (X-ray diffraction), STEM (scanning transmission electron microscopy) and SAW (surface acoustic waves). The results demonstrate the formation of a bcc a-Ta phase in the non-reactive Ta coating, which transitions to a mixture of crystalline tantalum and tantalum oxide phases for low oxygen concentrations while amorphous phases are observed for high oxygen levels. Ab-initio calculations of different Ta-O phases are in good agreement with the experimental results and reveal that the oxygen addition to the metallic Ta phase, leads to a distortion of the Ta crystal structure, causing a decrease in density and an increase of the elastic constants.
Author(s)
Almeida Alves, C.F.
Universität Minho / INL - International Iberian Nanotechnology Laboratory
Marques, Luís Silvino Alves
Universität Minho
Calderon, S.V.
INL - International Iberian Nanotechnology Laboratory
Ferreira, Paulo J.
INL - International Iberian Nanotechnology Laboratory / University of Texas at Austin / Universität Lissabon
Schneider, Dieter
Fraunhofer-Institut für Werkstoff- und Strahltechnik IWS  
Cavaleiro, Albano J.
Universität Coimbra
Carvalho, S.
Universität Minho / Universität Coimbra
Journal
Surface and coatings technology  
DOI
10.1016/j.surfcoat.2019.02.054
Additional full text version
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Language
English
Fraunhofer-Institut für Werkstoff- und Strahltechnik IWS  
Keyword(s)
  • Tantalum oxide coatings

  • magnetron sputtering

  • ab-initio

  • STEM

  • elastic modulus

  • LAwave

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