Abstract
A review of the presently available experimental information on the modulated phases of BCCD, which display a devil's-staircase behavior, is given. Some basic experimental results using methods of dielectric, high-frequency and optical spectroscopy are compiled and discussed. Data from X-ray and elastic and inelastic neutron scattering studies are also considered. This paper also includes some previously unpublished results, mainly about the role of lattice imperfections (doping, radiation-induced defects) on the sequence and stability of modulated phases and about solitons. Some problems hitherto unsolved or still under discussion are mentioned at the end of this article.