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 LiBC (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 degreesC under 50 bar of argon pressure. X-ray diffraction measurements indicate the formation of P6(3)/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 4300 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. (C) 2002 Elsevier Science Ltd. All rights reserved.