THERMOANALYTICAL STUDIES ON THE ORDER-DISORDER TRANSITION IN C-60 DOPED WITH C-70

C-60 crystals containing C-70 at various dopant levels, from 0 to 10%, have been grown via the novel method of 'solvent dilution'. Their crystallographic structures were examined with x-ray diffractometry, and their order-disorder phase transitions with differential scanning calorimetry. An extra HCP lattice structure was clearly seen in more highly doped C-60. On the other hand, both the phase transition temperature and the heat of transition decreased with rising C-70 concentration. This suppression of the order-disorder transition may be explained by a weakening of the correlation among C-60 molecules due to their dilution by the dopant.