Crystal Structure and Superconducting Properties of Hexagonal Lithium–Niobium Oxynitride

A hexagonal oxynitride (Li0.88□0.12)­Nb3.0(O0.13N0.87)4 was synthesized through ammonia nitridation of LiNb3O8. The structural analysis revealed that this oxynitride consists of alternate stacking of octahedral and prismatic layers with different Li/Nb ratios: significant amounts of Li and Nb atoms (Li/Nb = 43/57) coexist in the octahedral layer, while the prismatic site is preferentially occupied by Nb (Li/Nb = 3/97). A metallic behavior was accompanied by an abrupt drop of electrical resistivity at about 3 K. Furthermore, large diamagnetism and specific-heat anomaly were observed below this temperature, suggesting the appearance of superconductivity in the Li–Nb oxynitride.通过对LiNb3O8开展氨氮化反应，成功合成了六方氮氧化物(Li₀.₈₈□₀.₁₂)Nb₃.₀(O₀.₁₃N₀.₈₇)₄，其中□代表晶格空位。结构分析表明，该氮氧化物由具有不同Li/Nb比例的八面体层与棱柱层交替堆叠而成：八面体层内共存有大量Li与Nb原子（Li/Nb=43/57），而棱柱位点优先被Nb原子占据（Li/Nb=3/97）。该材料呈现金属性行为，并在约3 K时出现电阻率的突变下降。此外，在该临界温度以下可观测到显著的抗磁性与比热反常现象，提示该Li-Nb基氮氧化物体系中出现了超导性。