Carbon Vacancy Ordering in Zirconium Carbide Powder

Abstract

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.

Department(s)

Materials Science and Engineering

Comments

The current research was supported by the Ceramics Program in the US National Science Foundation (DMR 1742086).

Keywords and Phrases

neutron diffraction; nonstoichiometry; vacancies; vacancy ordering; zirconium carbide

International Standard Serial Number (ISSN)

0002-7820; 1551-2916

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2020 American Ceramic Society, All rights reserved.

Publication Date

01 Apr 2020

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