Carbon Vacancy Ordering in Zirconium Carbide Powder
Ordered carbon vacancies were detected in zirconium carbide (ZrCx) powders that were synthesized by direct reaction. Zirconium hydride (ZrH2) and carbon black were used as starting powders with the molar ratio of ZrH2:CÂ =Â 1:0.6. Powders were reacted at 1300°C or 2000°C. The major phase detected by x-ray diffraction (XRD) was ZrCx. No excess carbon was observed by transmission electron microscopy (TEM) in powders synthesized at either temperature. Ordering of the carbon vacancies was identified by neutron powder diffraction (NPD) and further supported by selected area electron diffraction (SAED). The vacancies in carbon-deficient ZrCx exhibited diamond cubic symmetry with a supercell that consisted of eight (2 x 2 x 2) ZrCx unit cells with the rock-salt structure. Rietveld refinement of the neutron diffraction patterns revealed that the synthesis temperature did not have a significant effect on the degree of vacancy ordering in ZrCx powders. Direct synthesis of ZrC0.6 resulted in the partial ordering of carbon vacancies without the need for extended isothermal annealing as reported in previous experimental studies.
Y. Zhou et al., "Carbon Vacancy Ordering in Zirconium Carbide Powder," Journal of the American Ceramic Society, vol. 103, no. 4, pp. 2891 - 2898, Blackwell Publishing Inc., Apr 2020.
The definitive version is available at https://doi.org/10.1111/jace.16964
Materials Science and Engineering
Keywords and Phrases
neutron diffraction; nonstoichiometry; vacancies; vacancy ordering; zirconium carbide
International Standard Serial Number (ISSN)
Article - Journal
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01 Apr 2020