Carbide and nitride phase characterization in a transition metal carbo-nitride using x-ray spectroscopy and atom probe tomography.

A multi-phase hafnium carbo-nitride was investigated by various analytical methods. Incomplete homogenization between mixed HfC-HfN starting powders subjected to hot isostatic pressing resulted in both carbon-rich and nitrogen-rich phases. The compositions of these two phases were quantified in detail by wavelength dispersive spectroscopy and atom probe tomography, with the atom probe tips having either a small or a large shank angle geometry. For each of the two phases, an agreement of the compositions obtained by wavelength dispersive spectroscopy and atom probe tomography was found. However, the quality of the mass spectrum and hit multiplicity (single hits) were generally higher for the carbon-rich as compared to the nitrogen-rich carbo-nitride. Though the atom probe tip geometry does not appear to influence the composition, the mass resolving power did improve with the larger shank angle geometry while the hit multiplicity deteriorated slightly. Finally, our results demonstrate that hafnium carbide requires less thermal assistance to field evaporate than hafnium nitride.