Study of statics and dynamics of staging in K and Rb GICs by in situ X-ray observation

Abstract

The static and dynamic properties of staging in alkali metal (K, Rb)-graphite intercalation compounds have been studied by in situ X-ray diffraction. Precise phase diagrams have been determined for the stages up to 7. Only pure stage structures have been observed. The stage dependence of Δμ( n), the stable range of a given stage, n, in chemical potential, is evaluated from the phase diagram and compared with the theoretical results. These observations are consistent with the screened electrostatic interaction for staging. Time dependent observation of the stage transformation reveals that only two phases of adjacent stages coexist throughout the process of the stage transformation and the c-axis disorder is insignificant even in the transition region. This indicates the small phase boundary region compared with the well-staged region. The dynamic process of the stage transformation is also discussed.