Synthesis and search for superconductivity in LiBC

Following the recent theoretical prediction of superconductivity in hole doped LiBC by Rosner et al [1], we have attempted to synthesise Li deficient LixBC (x = 1, 0.8, 0.6 and 0.4) and look for superconductivity in this system. Our synthesis procedure, following the recipe for MgB2, involves reaction of elemental components in a Ta crucible at 900o C under 50 bar of argon pressure. X-ray diffraction measurements indicate the formation of P63/mmc structure up to x=0.6. However, no diamagnetic signal or zero resistance, corresponding to the superconducting transition, was observed in the temperature range of 300 to 4 K. This is possibly related to the presence of disorder in the B-C stacking; evidence for which is suggested from a study of the vibrational modes of LixBC through infrared spectroscopy.