Study of the SmC alpha(*) phase in the Tokyo mixture by conoscopy using tilted cell

Song, Jangkun and Chandani, A. D. L. and Panarina, O. E. and Fukuda, Atsuo and Vij, Jagdish K. and Goertz, V. and Goodby, J. W. (2006) Study of the SmC alpha(*) phase in the Tokyo mixture by conoscopy using tilted cell. Ferroelectrics, 344 (1). pp. 285-291. ISSN 0015-0193

Abstract

We observed the existence of the SmC*(alpha) phase in the so-called Tokyo mixture, which has been used for studying V-shape switching by a number of research groups. Conoscopic observations, birefringence measurements using a set-up that employs a photo elastic modulator (PEM) and dielectric measurement were used for studying the behavior of the SmC*(alpha) phase. In particular, a conoscopic method using tilted cells was used to observe the conoscopy of the large tilt angle phase. We found that the tilted conoscopic method is very useful for analyzing large tilt smectic phases. The SmC alpha* phase was observed in a narrow temperature range from 63.0 degrees C to 63.4 degrees C. This is the first report of an observation of this phase in the Tokyo Mixture. It showed uniaxiality at low voltage but changed to biaxiality parallel to the electric field at high voltage in the conoscopic experiment. The absolute value of the biaxiality was quite high, up to 0.003, which means that the unwinding process of SmC*(alpha) is different from that of SmC*. This high parallel biaxiality implies the emergence of ferri-like structure, that is, co-existence of synclinic order and anticlinic order, during the field induced unwinding process.