Vacancy-driven extended stability of cubic metastable Ta-Al-N and Nb-Al-N phases

SURFACE & COATINGS TECHNOLOGY

卷:326

Article

Pacher, Ferdinand¹  Mayrhofer, Paul H.^1,2  Holec, David³ 

[1] TU Wien, Christian Doppler Lab Applicat Oriented Coating D, Inst Mat Sci & Technol, Getreidemarkt 9, A-1060 Vienna, Austria

[2] TU Wien, Inst Mat Sci & Technol, Getreidemarkt 9, A-1060 Vienna, Austria

[3] Univ Leoben, Dept Phys Met & Mat Testing, Franz Josef Str 18, A-8700 Leoben, Austria

关键词: Phase stability;    Ta-Al-N;    Nb-Al-N;    Density functional theory;    Vacancies;   

DOI  :  10.1016/j.surfcoat.2017.07.012

来源: Elsevier

【 摘 要 】

Quantum mechanical calculations had been previously applied to predict phase stability in many ternary and multinary nitride systems. While the predictions were very accurate for the Ti-AI-N system, some discrepancies between theory and experiment were obtained in the case of other systems. Namely, in the case of Ta-Al-N, the calculations tend to overestimate the minimum Al content necessary to obtain a metastable solid solution with a cubic structure. In this work, we present a comprehensive study of the impact of vacancies on the phase fields in quasi-binary TaN-AIN and NbN-AIN systems. Our calculations clearly show that presence of point defects strongly enlarges the cubic phase field in the TaN-AIN system, while the effect is less pronounced in the NbN-A1N case. The present phase stability predictions agree better with experimental observations of physical vapour deposited thin films reported in the literature than that based on perfect, non-defected structures. This study shows that a representative structural model is crucial for a meaningful comparison with experimental data. (C) 2017 Elsevier B.V. All rights reserved.

【 授权许可】

Free