POLYMORPHIC PHASE-TRANSITIONS AND MOLECULAR-MOTION IN PYRIDINIUM CHLOROCHROMATE

DTA, DSC, NMR and dielectric studies have been performed! for pyridini um chlorochromate over a wide temperature range. A sequence of four so lid-solid phase transitions was discovered, The in-plane complex reori entation of the cation is described by a three-well potential model wi th two correlation times, At higher temperatures one observes simultan eous cation tumbling and diffusion. Thus existence of a new ionic plas tic phase is revealed. The domain structure observed suggests ferroela stic properties of the compound. (C) 1997 Elsevier Science B.V.