Thermal expansion measurements of [formula omitted] mixed crystals

Abstract

The results of thermal expansion and room temperature powder X-ray diffraction measurements on (C 60) 1−x(C 70) x fullerene alloys are presented. Samples have been prepared by controlled condensation from the vapor phase. Strong anomalies in thermal expansion occur at the fcc to sc phase transition in C 60-rich, and hcp to distorted hcp one in C 70-rich crystals, respectively. The phase transition temperature diminishes with rising mixture ratio both on the C 60-rich ( ∼ −4K 1% C 70 ) and on the C 70-rich ( ∼ −20K 1% C 60 ) side of the phase diagram. This suggests the existence of an orientational glass phase on the C 70-rich side of the phase diagram (in agreement with thermal expansion measurements on sample with 70% C 70, which show no sign of the phase transitions at temperatures above 80 K).