Low-temperature x-ray powder diffraction studies of antimony pentachloride-intercalated graphite

Low-temperature x-ray diffraction has been used to study the effect that phase transitions, in various ${\mathrm{SbCl}}_5$ intercalated graphite compounds, have upon the $c$-axis spacing. The transition at 210 K appears not be be a single first-order transition on cooling. Heating through the phae transition causes expansion of the lattice, beyond the equilibrium value, which anneals out upon further warming. Higher-stage intercalation compounds display two such processes upon warming. The role of stacking disorder is discussed. A more probable cause is the internal pressure induced by hindered lateral motion of the intercalant which has been polymerized at low temperatures.