Synthesis and physical properties of LiBC intermetallics

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.