Rapid and Scalable Synthesis of Alkali Metal-Intercalated C$_{60}$ Superconductors

Abstract

Alkali metal-intercalated C$_{60}$, $A_3$$C_{60}$ ($A$ = K, Rb, Cs, and their combinations), holds significant potential for practical applications due to its high superconducting transition temperature (33 K), high upper critical field (900 kOe), and isotropic superconductivity. However, application-oriented research has been limited by the lack of an efficient $A_3$$C_{60}$ synthesis process. In this study, we demonstrate a rapid and scalable synthesis of $A_3$$C_{60}$ ($A$ = K, Rb, and Cs$_{1/3}$Rb$_{2/3}$) via direct mixing of $A$ and C$_{60}$, realizing the fabrication of high-quality sintered $A_3$$C_{60}$ pellets within just 1 hour of heating at 200-300{\deg}C. The pellets exhibited large superconducting shielding volume fractions with sharp transitions, and the relationship between the lattice constant and transition temperature was in good agreement with previous reports. This direct mixing method enables simple and rapid production of large quantities of $A_3$$C_{60}$, which is expected to accelerate research into applications such as superconducting wires and bulk magnets.