We report the synthesis of a polycrystalline specimen of TiC_1−x under high-pressure and high-temperature (HPHT) conditions. The carbon vacancy, crystal structure, Vicker hardness, elastic constants, and bond features of the synthesized specimen were investigated. Though the specimens were synthesized with stoichiometric ratio at high pressure, a robust carbon vacancy was observed using energy dispersive and X-ray photoelectron spectrum. TiC_1−x exhibits almost the highest asymptotic Vickers hardness in transition-metal light-element (TMLE) compounds. In this study, using Vickers hardness characterization, the asymptotic hardness was found to be 27.1 GPa. This exceeds the hardness of most transition metal borides with high boron concentrations. Based on the first-principles calculation of the Mulliken population of Ti-C bonds, the intrinsic high Vickers hardness of TiC_1−x is attributed to the combination of covalent Ti-C bonds and the optimized eight-valence-electron structure, while the extrinsic contribution comes from the harden effect of carbon defects. This work demonstrates that a higher concentration of light elements or a higher-dimensional light element framework is not the critical factor for higher hardness, and carbon vacancy is another way to strengthen the crystal structure.

我们报告了在高温高压（HPHT）条件下TiC _1-x的多晶试样的合成。研究了合成样品的碳空位，晶体结构，维氏硬度，弹性常数和键合特征。尽管在高压下以化学计量比合成了样品，但使用能量色散和X射线光电子能谱观察到了稳健的碳空位。TiC _1-x在过渡金属轻元素（TMLE）化合物中表现出几乎最高的渐近维氏硬度。在这项研究中，使用维氏硬度表征，发现渐近硬度为27.1 GPa。这超过了大多数具有高硼浓度的过渡金属硼化物的硬度。根据Ti-C键的Mulliken族的第一性原理计算，TiC _1-x的固有高维氏硬度这归因于共价Ti-C键和优化的八价电子结构的结合，而外在贡献来自碳缺陷的硬化效应。这项工作表明，较高浓度的轻元素或较高尺寸的轻元素框架不是较高硬度的关键因素，而碳空位是增强晶体结构的另一种方法。