ELASTIC BEHAVIOR OF POLYCRYSTALLINE BAVS3 IN THE TEMPERATURE-RANGE 40-K TO 350-K

The longitudinal and transverse ultrasonic wave velocities of polycrystalline BaVS3 have been measured over a temperature range 40 K to 350 K. At 258 K the material undergoes a structural phase transition from a hexagonal to an orthorhombic form. Although the displacement of ions which occurs at the transformation is not so large, marked changes in the sound velocities as well as enhanced sound attenuation are observed at the transition. By analogy with the case of other perovskite-like compounds, the present observations are qualitatively explained by considering the interaction of “soft-mode” phonons with the elastic distortions produced by the phase transition. © 1979 The Japan Society of Applied Physics.