Abstract
We have performed thermal conductivity measurements on C60 and C70 crystals grown by sublimation. For single crystal C60, the thermal conductivity k is ∼0.4 W/m K at room temperature and is nearly temperature independent down to 260K. We observed a sharp orientational phase transition at 260K, indicated by a 25% jump in k. Below 90K, k is time dependent, which manifests itself as a shoulder-like structure at ∼85K. The temperature and time dependence of k below 260K can be described by a simple model which accounts for the thermally activated hopping of C60 molecules between two nearly degenerate orientations, separated by an energy barrier of ∼240 meV. It is found that solvents have a strong influence on the physical properties of C70 crystals. For solvent-free C70 crystal, k is about constant above 300K. There is a broad first-order phase transition in k at 300K with a 25% jump. We associate this transition with the aligning of the fivefold axes of the C70 molecules along the c-axis of the hexagonal lattice. Upon further cooling, k increases and is time independent.
Similar content being viewed by others
References
W. Krätschmer, D. Lamb, K. Fostiropoulos, D.R. Huffman: Science 347, 354 (1990)
X.-D. Xiang, J.G. Hou, G. Briceno, W.A. Vareka, R. Mostovoy, A. Zettl, V.H. Crespi, M.L. Cohen: Science 256, 1190 (1992)
J. Li, S. Komiya, T. Tamura, C. Nagasaki, J. Kihara, K. Kishio, K. Kitazawa: Physica C 195, 205 (1992)
P.A. Heiney, J.E. Fischer, A.R. McGhie, W.J. Romanow, A.M. Denenstein, J.P. McCauley Jr., A.B. Smith III, D.E. Cox: Phys. Rev. Lett. 66, 2911 (1991)
M. Moret, P.A. Albouy, V. Agafonov, R. Ceolin, D. Andre, A. Dworkin, H. Szwarc, C. Fabre, A. Rassat, A. Zahab, P. Bernier: J. Phys. 1 (France) 2, 511 (1992)
R. Tycko, G. Dabbagh, R.M. Fleming, R.C. Haddon, A.V. Makhija, S.M. Zahurak: Phys. Rev. Lett. 67, 1886 (1991)
W.I.F. David, R.M. Ibberson, T.J.S. Dennis, J.P. Hare, K. Prassides: Europhys. Lett. 18, 219 (1992)
X.D. Shi, A.R. Kortan, J.M. Williams, A.M. Kini, B.M. Savall, P.M. Chaikin: Phys. Rev. Lett. 68, 827 (1992)
G.B. Alers, B. Golding, A.R. Kortan, R.C. Haddon, F.A. Theil: Science 257, 511 (1992)
T. Atake, T. Tanaka, H. Kawaji, K. Kikuchi, K. Saito, S. Suzuki, I. Ikemoto, Y. Achiba: Physica C 185, 427 (1991)
R.C. Yu, N.H. Tea, M.B. Salamon, D. Lorents, R. Malhotra: Phys. Rev. Lett. 68, 2050 (1992)
M. Chung, Y. Wang, J.W. Brill, X.-D. Xiang, R. Mostovoy, J.G. Hou, A. Zettl: Phys. Rev. B 45, 13831 (1992)
T. Matsuo, H. Suga, W.I.F. David, R.M. Ibberson, P. Bernier, A. Zahab, C. Fabre, A. Rassat, A. Dworkin: Solid State Commun. 83, 711 (1992)
J.P. Lu, X.-P. Li, R.M. Martin: Phys. Rev. Lett. 68, 1551 (1992)
M. Sprik, A. Cheng, M.L. Klein: J. Phys. Chem. 96, 2027 (1992)
G.B.M. Vaughan, P.A. Heiney, J.E. Fischer, D.E. Luzzi, D.A. Ricketts-Foot, A.R. McGhie, Y.-W. Hui, A.L. Smith, D.E. Cox, W.J. Romanow, B.H. Allen, N. Coustel, J.P. McCauley Jr., A.B. Smith III: Science 254, 1350 (1991)
M.A. Verheijen, H. Meekes, G. Meijer, P. Bennema, J.L. deBoer, S. van Smaalen, G. van Tendeloo, S. Amelinckx, S. Muto, J. Van Landuyt: Chem. Phys. (in press, 1992)
D.A. Neumann, J.R.D. Copley, R.L. Cappelleti, W.A. Kamitakahara, R.M. Lindstrom, K.M. Creegan, D.M. Cox, W.J. Ramanow, N. Coustel, J.P. McCauley Jr., N.C. Maliszewskyj, J.E. Fischer, A.B. Smith III: Phys. Rev. Lett. 67, 3808 (1991)
K. Ghiron, N. Tea, M.B. Salamon, S. Keofod, J. Shapley: Unpublished
T. Atake, T. Tanaka, H. Kawaji, K. Kikuchi, K. Saito, S. Suzuki, Y. Achiba, I. Ikemoto: Chem. Phys. Lett. 196, 321 (1992)