Synthesis and physical properties of LiBC intermetallics

TL;DR

This study synthesized polycrystalline LiBC compounds, investigated their physical properties, and found they are semiconductors without superconductivity, contrary to theoretical predictions of high-Tc superconductivity.

Contribution

It provides experimental synthesis and characterization of LiBC, revealing its semiconducting nature and lack of superconductivity, challenging previous theoretical predictions.

Findings

LiBC samples are semiconductors with an activation energy of 18 meV.

No superconductivity was observed down to 2 K.

Lattice constants vary systematically with composition.

Abstract

Polycrystalline samples of LiBC compounds, which were predicted as possible candidate for high-Tc superconductivity, have been synthesised by a flux method and investigated by means of electrical resistivity and magnetic susceptibility. Scanning electron microscopy and X-ray diffraction patterns showed a plate-like morphology and a single-phase nature of LiBC samples for starting composition of Li1.25BC (flux composition). The lattice constants a, c display a systematic variation with x and has maximum volume of the hexagonal unit cell at x = 1.25. Electrical resistivity measurements revealed an extrinsic semi-conducting behaviour of the single-phase LiBC with an activation energy of 18 meV and a maximum specific resistivity of 2.5 Wcm at 300 K. In contrast to the theoretical prediction of high Tc, no superconducting features were detected down to 2 K both, by measurements of electrical resistivity and magnetic susceptibility.