Crystal structure and superconducting properties of hexagonal lithium-niobium oxynitride

TL;DR

This study reports the synthesis, detailed crystal structure, and discovery of superconductivity at 3 K in a hexagonal lithium-niobium oxynitride, revealing layered atomic arrangements and metallic behavior.

Contribution

It provides the first detailed structural characterization and superconducting property analysis of a hexagonal lithium-niobium oxynitride.

Findings

Superconductivity observed at about 3 K.

Layered crystal structure with distinct Li/Nb ratios.

Metallic electrical behavior above the transition.

Abstract

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.