Elsevier

Scripta Materialia

Volume 155, October 2018, Pages 5-10
Scripta Materialia

Regular article
Substoichiometry and tantalum dependent thermal stability of α-structured W-Ta-B thin films

https://doi.org/10.1016/j.scriptamat.2018.06.005Get rights and content

Abstract

Physical vapor deposited (PVD) WB2 thin films crystallize in the α-AlB2-prototype structure rather than in their thermodynamically stable ω-W2B5-z-prototype structure. Contrary to the majority of α-AlB2-type transition metal diborides (TMB2), α-WB2 exhibits a more ductile character. Combining density functional theory and sophisticated experiments, we show that the stability of α-WB2 thin films is basically influenced by point defects such as vacancies present in PVD materials. With the help of α-TaB2 (one of the most ductile TMB2 with high preference for α-AlB2-type), the thermally driven decomposition and phase transformation of α-W1-xTaxB2-z to the ω-W2B5-z-type can be shifted to temperatures above 1200 °C.

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Acknowledgement

The financial support by the Austrian Federal Ministry of Economy, Family and Youth and the National Foundation for Research, Technology and Development is gratefully acknowledged. We also thank for the financial support of Plansee Composite Materials GmbH and Oerlikon Balzers, Oerlikon Surface Solutions AG. SEM and XRD investigations were carried out using facilities of the XRC and USTEM centers of TU Wien, Austria. We thank the Vienna Scientific Cluster for the attribution of computation

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