Phase transitions of -intercalated crystals
Laboratory of Crystallography, University of Bayreuth, D-95440 Bayreuth, Germany
2 Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
3 Department of Molecular and Laser Physics, University of Nijmegen, Toernooiveld, NL-6525 ED Nijmegen, The Netherlands
Accepted: 11 June 1998
We report the temperature dependence of the specific heat of , and the temperature dependence of the lattice parameter, as determined by X-ray powder diffraction. A first-order phase transition and a glass transition are found to occur at temperatures below the corresponding transition temperatures of pure . The transition temperatures depend on x. Specific-heat measurements on a sample with show the orientational ordering transition at K and the glass transition at . Contrary to pure , the temperature dependence of the lattice parameter of () does not show an anomaly at the glass transition, which is explained by the already expanded lattice of . The energy difference between major and minor orientations is determined as 19.1 meV.
PACS: 61.48.+c – Fullerenes and fullerene-related materials / 65.40.+g – Heat capacities of solids / 64.70.Pf – Glass transitions
© EDP Sciences, 1998