Na2C60 is believed to be an electron-hole counterpart of the
Mott-Jahn-Teller insulator A(4)C(60) salts. We present a study
of infrared, ESR, NMR spectroscopy, x-ray diffraction, chemical
composition and neutron scattering on this compound. Our
spectroscopic results at room temperature can be reconciled in a
picture of segregated regions of the size 3-10 nm. We observe a
significant insulating C-60 phase and at least two more phases,
one of which we assign to metallic Na3C60. The separation
disappears on heating by jump diffusion of the sodium ions,
which we followed by neutron scattering. Above similar to 460 K
we see infrared spectroscopic evidence of a Jahn-Teller
distorted C-60(2-) anion.
