In situ study of the high pressure high-temperature stability field of TaN and of the compressibilities of ϑ-TaN and TaON

• Published in: High pressure research 2013-08, Vol.33 (3), p.633-641
• Main Authors: Friedrich, A., Morgenroth, W., Bayarjargal, L., Juarez-Arellano, E. A., Winkler, B., Konôpková, Z.
• Format: Article
• Language: English
• Subjects: high pressure; laser-heated diamond anvil cell; phase stability; tantalum nitride; tantalum oxynitride; X-ray diffraction
• ISSN: 0895-7959; 1477-2299
• DOI: 10.1080/08957959.2013.813943

The high pressure high-temperature stability of tantalum mononitrides was investigated at 8-23.5 GPa and 1400-3500 K by in situ powder synchrotron X-ray diffraction using the laser-heated diamond anvil cell and ϵ-TaN as starting material. The transformation from ϵ-TaN to ϑ-TaN was observed and ϑ-TaN was confirmed as the stable high-(p, T) tantalum mononitride. At temperatures above 3000 K at 16-23.5 GPa, the formation of a novel quenchable high pressure high-temperature phase was observed. Under nitrogen excess ϵ-TaN reacted with nitrogen to the high-(p, T) phase η-Ta 2 N 3 as the main stable phase at 8-13 GPa and about 2000 K. This behaviour is similar to the reaction of pure Ta with nitrogen at high-(p, T) conditions. In addition, we have determined the bulk moduli of ϑ-TaN (B=360(15) GPa), which is less compressible than ϵ-TaN and η-Ta 2 N 3 , and of TaON (B=267(8) GPa).