NOVEL RARE-GAS INTERSTITIAL FULLERENES OF C-70

The formation and characterisation of the rare gas interstitial compou nds of argon, krypton and xenon with C-70 are presented. The materials were produced by hot-isostatically pressing (HIPing) powdered samples of C-70 at a temperature of 400 degrees C and under a surrounding rar e gas pressure between 170 and 200 MPa for similar to 12 h. The materi als were analysed by thermogravimetric analysis (TGA) and X-ray powder diffraction (XRD). It appears that under the HIP conditions used we w ere able to saturate all octahedral sites of the C-70 lattice (experim ental error 5- 10%), giving the rare gas stoichiometric materials Ar1C 70, Kr1C70 and Xe1C70. The C-70 rare gas fullerenes were found to be m ore susceptible to loss of rare gas, compared with the corresponding C -60 materials, although the relative stabilities followed the same pat tern. with heavier intercalated rare gases being lost more slowly. The argon is lost very easily (within a few days) whereas the krypton and xenon C-70 fullerenes were found to be stable at room temperature for several months, with some loss from the krypton fullerene. (C) 1998 E lsevier Science Ltd. All rights reserved.