An investigation of the longrange and local structure of substoichiometric zirconium carbide sintered at different temperatures Dhan-sham B. K. Rana 1* , Eugenio Zapatas Solvas 2 , William e. Lee 2 & ian farnan 1 Zrc 1−x (sub-stoichiometric zirconium carbide), a group IV transition metal carbide, is being considered for various high temperature applications. Departure from stoichiometry changes the thermo-physical response of the material. Reported thermo-physical properties exhibit, in some cases, a degree of scatter with one likely contributor to this being the uncertainty in the C/Zr ratio of the samples produced. Conventional, methods for assigning C/Zr to samples are determined either by nominal stochiometric ratios or combustion carbon analysis. In this study, a range of stoichiometries of hotpressed ZrC 1−x were examined by SEM, XRD, Raman spectroscopy and static 13 C NMR spectroscopy and used as a basis to correct the C/Zr. Graphite, amorphous, and ZrC 1−x carbon signatures are observed in the 13 C NMR spectra of samples and are determined to vary in intensity with sintering temperature and stoichiometry. In this study a method is outlined to quantify the stoichiometry of ZrC 1−x and free carbon phases, providing an improvement over the sole use and reliance of widely adopted bulk carbon combustion analysis. We report significantly lower C/Zr values determined by 13 C NMR analysis compared with carbon analyser and nominal methods. Furthermore, the location of carbon disassociated from the Zrc 1−x structure is analysed using SEM and Raman spectroscopy. ZrC 1−x (sub-stoichiometric zirconium carbide), is under consideration for its use in generation IV nuclear fuel coatings due to its favourable mechanical, thermal, neutronic, and fission product retention properties 1-4. This combination of characteristics is derived from the combination of its metallic electronic properties and its ceramic properties 5. ZrC crystallises in the rocksalt structure with carbon atoms located in the octahedral interstitial sites. When carbon is removed from the ZrC structure, significant changes are seen in the physical and thermal properties. Scatter in reported data exists in the variation of the physical properties with the atomic C/Zr ratio. The scatter in the data potentially arises due to the combination of two factors: inaccurate composition measurements (C/Zr ratio) resulting in misreferenced physical properties; and the contribution of interstitial impurities such as oxygen and nitrogen leading to a range values for several themo-physical properties. Non-monotonic trends in material properties have been observed for physical properties, such as the lattice parameter. Assuming the sub-stochiometric material is comprised exclusively of ZrC and no contaminant species the configuration ordering of carbon atoms as the concentration of vacancies increases may be a contributing factor to the occurrence of these non-monotonic trends. As understanding of how these vacancies interact and how this affects material properties is c...