TEMPERATURE-DEPENDENCE OF DOMAIN-STRUCTURE OF AMMONIUM ROCHELLE SALT

X-ray studies on ammonium Rochelle salt have been made mainly around t he phase transition temperature by Weissenberg photographic method wit h an imaging-plate. We observed positions and intensities of Bragg ref lections as a function of temperature. Spontaneous strain occurs below the phase transition temperature and the strain has no temperature de pendence. Superlattice reflections occur at the phase transition tempe rature and its intensities gradually increase with decreasing temperat ure. The order parameter of the phase transition seems not to be the s pontaneous strain but to be the change of the atomic arrangements in t he unit cell.