Signs of Possible High-Temperature Superconductivity in Graphite Intercalated with Lithium-Based Alloys

Abstract: We report experimental results indicating possible high-temperature superconductivity in graphite intercalation compounds synthesized with lithium-based alloys. Temperature-dependent measurements of magnetization, trapped magnetic flux, and electrical resistance reveal transitions with critical temperatures (Tc) in the range of 240-350 K at ambient pressure, depending on intercalation metals and conditions. The highest Tc values and largest high-Tc fractions (< 0.1 %) were observed in graphite samples intercalated with ternary Sr-Ca-Li alloy. Our results and analyses suggest that the observed transitions originate from local superconductivity rather than intrinsic magnetic properties of the intercalated graphite, which may be an alternative explanation. Accordingly, we propose and intend to pursue further investigations to test and confirm the nature of the observed high-Tc transitions, and to obtain larger high-Tc fractions by optimizing the intercalation materials and methods.