Huang Ming-Xing, Fan Changzeng, Xu Bo, Hou Jingyu, Shao Xi, Weng Xiao-Ji, Zhang Xiang, Hu Wentao, Gao Yufei, Wang Lin, Zhao Zhisheng, Yang Guochun, Zhang Dongzhou, Wang Yanbin, Liu Zhongyuan, Zhou Xiang-Feng, Tian Yongjun
Center for High Pressure Science, State Key Laboratory of Metastable Materials Science and Technology, <a href="https://ror.org/02txfnf15">Yanshan University</a>, Qinhuangdao 066004, China.
Key Laboratory for Microstructural Material Physics of Hebei Province, School of Science, <a href="https://ror.org/02txfnf15">Yanshan University</a>, Qinhuangdao 066004, China.
Phys Rev Lett. 2024 Sep 27;133(13):136301. doi: 10.1103/PhysRevLett.133.136301.
Copper and boron seldom engage in reaction at ambient pressure. The few reports on copper-doped boron compounds that exist in the literature often lack definitive stoichiometry. Here, we report successful synthesis of Cu_{2-δ}B_{25} single crystals (δ∼0.03, indicating Cu understoichiometry) via a high-pressure melting method using copper and β-rhombohedral boron as precursors. Crystals thus synthesized are characterized by a tetragonal boron sublattice, within which Cu atoms are either partially or fully situated at different interstices between B_{12} icosahedra. The crystals possess a high Vickers hardness of 26.5 GPa and an unusually high electrical conductivity of 1.19×10^{5} S/m-the highest conductivity among the icosahedron-based borides. Hall measurements reveal a notable p-n conduction type transition around 30 GPa. This transition, alongside the remarkable conductivity, is potentially modulated by the copper content and its valence states within the structure. The synthesis of Cu_{2-δ}B_{25} not only broadens the spectrum of hard materials but also opens new avenues for innovative modulation of electronic properties in boron-rich compounds, with promising technological implications.
在常压下，铜和硼很少发生反应。文献中关于铜掺杂硼化合物的报道寥寥无几，且往往缺乏明确的化学计量比。在此，我们报道了通过以铜和β - 菱形硼为前驱体的高压熔融法成功合成了Cu₂₋₈B₂₅单晶（δ ∼ 0.03，表明铜存在化学计量不足）。如此合成的晶体具有四方硼亚晶格，其中铜原子部分或全部位于B₁₂二十面体之间的不同间隙中。这些晶体具有26.5 GPa的高维氏硬度和1.19×10⁵ S/m的异常高电导率——这是基于二十面体的硼化物中最高的电导率。霍尔测量表明在30 GPa左右存在明显的p - n导电类型转变。这种转变以及显著的电导率可能受结构内铜含量及其价态的调节。Cu₂₋₈B₂₅的合成不仅拓宽了硬质材料的范围，还为富硼化合物电子性质的创新调控开辟了新途径，具有广阔的技术应用前景。
