Synthesis and structural analysis of nonstoichiometric ternary fulleride K (1.5) Ba (0.25) CsC (60)

The existence of cation-vacancy sites in fullerides might lead to long-range ordering and generate a new vacancy-ordered superstructure. The purpose of this work is to search whether or not long-range ordering of vacant tetrahedral sites, namely superstructure emerges in nonstoichiometric K (1.5) Ba (0.25) CsC (60) fulleride. Therefore, K (1.5) Ba (0.25) CsC (60) with cation-vacancy sites is synthesized using a precursor method to avoid inadequate stoichiometry control and formation of impurity phases within the target composition. For this purpose, first, phase-pure K (6) C (60) , Ba (6) C (60) and Cs (6) C (60) precursors are synthesized. Stoichiometric quantities of these precursors are used for further reaction with C (60) to afford K (1.5) Ba (0.25) CsC (60) . Rietveld analysis of the high-resolution synchrotron X-ray powder diffraction data of the precursors and K (1.5) Ba (0.25) CsC (60) confirms that K (6) C (60) , Ba (6) C (60) and Cs (6) C (60) are single-phase and they crystallize in a body-centered-cubic structure ( Im 3) as reported in the literature. The analysis also shows that K (1.5) Ba (0.25) CsC (60) phase can be perfectly modeled using a face-centered cubic structure. No new peaks appear which could have implied the appearance of a superstructure. This suggests that there is no long-range ordered arrangement of vacant tetrahedral sites in K (1.5) Ba (0.25) CsC (60) .