Mass spectrometric investigations of the K/C60 binary system

D.Yu. Borisova, A.A. Mavrin, L.N. Sidorov, E.V. Skokan, J.G. Edwards, F.M. Spiridonov, A.Ya. Borshchevsky, I.N. Ioffee

"Fullerenes. Recent advances in the chemistry and physics of fullerenes and related materials", edited by Karl M.Kadish and Rodney S. Ruoff, published by: the Electrochemical Society, Inc. 10 South Main Street, Pennington, New Jersey , v.97-14, pp. 956-968, (1997)

ABSTRACT. Knudsen cell mass spectrometry was used to study K/C60 binary system. Powder KxC60 samples with nominal stoichiometries 0.9, 1.57, and 3.14 were synthesized, characterized by X-ray powder diffraction, and the vapor pressures of C60 and/or potassium were measured over the samples in the temperature range 600-970 K. A range of homogeneity was observed for each phase, including the superconducting one, K3C60, and the vapor pressure minimum in K/C60 system was found to lie within the homogeneity range of K3C60 phase with potassium vacancies. Gibbs energies of formation of KC60 and K3C60 from K(l) and C60(s) were calculated from the experimental data. KC60(g) was detected in the equilibrium vapor over KxC60 with 1<x<3, and the Gibbs energy of formation of KC60(g) from K(g) and C60(g) was calculated directly from the experimental data/

Laboratory of Thermochemistry