New data on the phase transition in phenanthrene

The phase transition in phenanthrene C14H10 crystals at 72°C has been investigated. The measurements of dielectric, pyroelectric, optical and acoustical properties were performed and are reported here. The preliminary refinement of the x-ray data shows that the high temperature phase is orientationally disordered. The results indicate that the transition is probably pseudoproper ferroelectric with a symmetry change 2/m - 2.