Synthesis and Properties of Alkali Metal Fulleride Solids

2 Synthesis and Properties of Alkali Metal Fulleride Solids 

The discovery of superconductivity [105] in alkali metal doped attracted the attention of a broad cross-section of the scientific community. The composition of the first alkali metal doped fullerene was determined to be [106,107]. In this compoimd, the transition to a superconducting state occurs at = 19.3 K [106]. In a short time, a large variety of alkali metal fullerides M Cgo have been synthesized and studied with respect to their solid-state properties [1, 106-114]. Thereby, the stoichiometries of as well as the alkali metal with M = Na, K, Rb, Cs have 

This direct method is a convenient route, especially for saturation-doped fullerides MgCgo-A facile control of the alkali metal fulleride stoichiometry of M Cgg (M = K, 

Cs) can be obtained using vapor-transport techniques [115]. Thereby, a weighed amoimt of Cjq is treated with a large excess of the alkali metal at 225 °C under vacuum. This procedure leads to the saturation-doped products MgC g. To these fullerides a specific amount of Cjq is added to give the desired stoichiometry. The process of the formation of is completed after a subsequent annealing 

The synthesis of M Cgo (M = Na, n = 2, 3 M = K, n = 3) has been achieved by the reaction of solid Cjq with solid MH or MBH4 [116]. The advantage of these reactions is the easier handling of small quantities of MH or MBH4 compared with alkali metals. As a source for alkali metals, binary alloys of the type CsM (M = Hg, Tl, Bi) can also be used [109]. However, the heavy metals partly co-intercalate into the Cgo lattice [115, 117]. 

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