Synthesis and search for superconductivity in LiBC

Following the recent theoretical prediction of superconductivity in hole doped LiBC by Rosner et al. [Phys. Rev. Lett. 88 (2002) 127001], we have attempted to synthesize Li deficient LixBC (x=1, 0.8, 0.6 and 0.4) and looked for superconductivity in this system. Our synthesis procedure, following the recipe for MgB2, involves reaction of elemental components in a Ta crucible at 900 °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, were observed in the temperature range of 4–300 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.