Stability and Phase Formation in the (Li/Na)6C60–H Systems Studied by Neutron Scattering

Small-angle neutron scattering combined with powder neutron diffraction was employed to study the phase formation upon absorption/desorption of hydrogen gas in Li- and Na-intercalated fullerides. The comparative system analysis, addressing changes in the sample phase compositions and the morphology of powders, revealed a higher degree of complexity in the Na-based samples. Results also showed that the disappearance of crystalline lithium/sodium hydride during desorption was accompanied by an increased surface roughness in both systems, most likely because of the formation of a local surface strain. Furthermore, an increased specific internal surface of the studied materials upon subsequent deuterium absorption/desorption cycles was demonstrated. This could indicate moderate fracturing of crystallites.