Order-Disorder Mechanism and a Phenomenological Model in (Bi,Pb)-Sr-Ca-Cu-O

We established a relationship between the structures of the bismuth high T$\text{}_{c}$ superconducting compounds and a symmetry of disordered perovskite type. This description which we propose, leads to considering the structures of these materials in terms of a commensurate superstructure obtained from a latent perovskite structure of space group Im3m. A phenomenological model was elaborated in order to describe the two types of modulations realized in these compounds.