Effects of Mechanical Grinding on C₆₀ And Ca₅C₆₀ Superconductor

Abstract

The effects of mechanical grinding on polycrystalline C₆₀ and Ca₅C₆₀ superconductor are examined. It has been found that mechanical grinding may severely degrade phases of C₆₀ (fcc) and Ca₅C₆₀ (sc). The grinding destroys the long-range ordering of crystals and produces a partial amorphous state. The damage of crystal leads to the disappearance of superconductivity for Ca₅C₆₀. The samples with an amorphous phase can be recrystallized by annealing at 600°C for pure C₆₀ and Ca₅C₆₀. Magnetic susceptibility measurements indicated that the superconductivity of the degraded sample did not recover easily to the initial state.