DISTRIBUTION OF K IONS IN INTERMEDIATE KC60

Intermediate KC60 formed from the homogeneous KC60 phase at 400 K is i nvestigated by differential scanning calorimetry, x-ray diffraction, d e resistivity, electron-spin resonance (ESR), and magnetic ac suscepti bility. We show that in intermediate KC60 the C-60 sublattice is conti nuous over large distances but the K ions separate into small K3C60 an d K-free C-60 regions. ESR shows a large volume fraction of supercondu cting K3C60 The K3C60 phase is finely distributed and the magnetic-hel d exclusion is small. K3C60 regions are compressed and K-free regions are expanded with-respect to the corresponding bulk phases. The compre ssion decreases the superconducting critical temperature (T-c) from 19 to 16 K. The expansion of the K-free C-60 regions decreases the orien tational ordering transition temperature (at 260 K) by 10 K.