Characterization of zirconium carbides using electron microscopy, optical anisotropy, Auger depth profiles, X-ray diffraction, and electron density calculated by charge flipping method

Samples with five different zirconium carbide compositions (C/Zr molar ratio=0.84, 0.89, 0.95, 1.05, and 1.17) have been fabricated and studied using a variety of experimental techniques. Each sample was zone refined to ensure that the end product was polycrystalline with a grain size of 10–100 μm. It was found that the lattice parameter was largest for the x=0.89 composition and smallest for the x=1.17 total C/Zr composition, but was not linear; this nonlinearity is possibly explained using electron densities calculated using charge flipping technique. Among the five samples, the unit cell of the ZrC0.89 sample showed the highest electron density, corresponding to the highest carbon incorporation and the largest lattice parameter. The ZrC0.84 sample showed the lowest carbon incorporation, resulting in a larger number of carbon vacancies and resultant strain. Samples with larger carbon ratios (x=0.95, 1.05, and 1.17) showed a slight decrease in lattice parameter, due to a decrease in electron density. Optical anisotropy measurements suggest that these three samples contained significant amounts of a graphitic carbon phase, not bonded to the Zr atoms.

Characterization of zirconium carbides using electron microscopy, optical anisotropy, Auger depth profiles, X-ray diffraction, and electron density calculated by the charge flipping method. Figure optionsDownload as PowerPoint slideHighlights
► The lattice parameter variation: ZrC0.89>ZrC0.84>ZrC0.95>ZrC1.05>ZrC1.17.
► Surface oxygen with no correlation to the lattice parameter variation.
► ZrC0.89 had highest electron densities correspond to highest carbon incorporation.
► Second highest lattice parameter in ZrC0.84 due to strain.
► Unit cell electron density order: ZrC0.95>ZrC1.05>ZrC1.17.