Lattice expansion and phase stability in nanocrystalline titanium thin films

ABSTRACT

Crystallite-size-dependent lattice expansion of the hcp Ti phase has been observed by X-ray diffraction of polycrystalline Ti thin films. X-ray line profile analysis (XLPA) revealed a systematic reduction of crystallite size in the hcp Ti phase with decreasing film thickness. Increase of specific volume (i.e. volume/atom) of the hcp Ti phase with decreasing crystallite size has confirmed such lattice expansion. The observed lattice expansion has been simulated using an existing theoretical model after appropriately incorporating a crystallite-size-dependent width of the grain boundaries. It is further revealed that decreasing crystallite size and accompanying lattice expansion leads to lattice instability of the hcp Ti phase and eventually to a hcp-fcc phase transformation of elemental Ti in these thin films as reported earlier by the author.

KEYWORDS:

• Lattice expansion
• phase transformation
• titanium
• crystallites
• hcp
• fcc
• X-ray diffraction

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

J. Chakraborty

Dr. J. Chakraborty is the senior principal scientist at the Materials engineering division, National metallurgical laboratory under the ‘Council of scientific & industrial research’, India. He obtained his Ph.D degree from the ‘Max-Planck Institute for Metals Research’, Stuttgart, Germany in 2005. His research interests are diffusion and phase transformation in metallic thin films and nanomaterials, X-ray diffraction analysis of phase transformation, microstructure and residual stresses in thin films and bulk materials. He has more than twenty years of research experience including industrial R&D and academia.