Relaxation dynamics in molecular alloys. II. Supercooled (C2F6)1−x (CClF3)x plastic crystals

Dielectric measurements on quenched (C2F6)1−x (CClF3)x fluorocarbon alloys are reported. In a wide concentration range, rapid cooling prevents these samples from unmixing and the plastic phase, characterized by translational order and orientational disorder, can be supercooled. The relaxation dynamics of crystals with x=0.32 is examined in detail. For temperatures below 50 K it exhibits a dominant primary and indications of secondary relaxation, i.e., typical features of glasses. The α-relaxation process is parametrized in terms of a modified Vogel–Fulcher law. Using this representation, (C2F6)0.68(CClF3)0.32 can be characterized as fragile glass according to Angell’s classification scheme.