The crystal growth of transition metal interstitial compounds by a floating zone technique

• Published in: Journal of crystal growth 1972-05, Vol.13-14, p.693-697
• Main Authors: Billingham, J., Bell, P.S., Lewis, M.H.
• Format: Article
• Language: English
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/0022-0248(72)90543-X

A floating zone technique for the preparation of large high purity crystals of vanadium carbide, oxide and nitride with controlled stoichiometry is described. An essential feature of the process is the provision of a facility which enables growth under positive ambient gas pressures (up to 20 atm) to be carried out. Inert gas atmospheres are used to reduce vanadium vaporisation losses in vanadium carbide and oxide and so enable closer compositional control to be achieved, while the nitrides are grown under similar pressures of nitrogen and helium to reduce nitrogen losses. Zone levelling has enabled large single crystals of vanadium monocarbide (VC) with differing and closely controllable compositions to be produced. Vanadium monoxide crystals were grown over the whole cubic stoichiometry range but in the vanadium nitrogen system single phase cubic vanadium mononitride (VN) could not be produced and the microstructure of the alloy of highest nitrogen content consisted of a eutectic of the cubic VN and the hexagonal divanadium nitride (V2N) phases. Finally, in addition to the usual chemical and optical microstructural examination, electron microscopy and electron diffraction have been used to characterise the type and extent of the defect structures which are present in all three alloy systems studied.