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.