(Bi,Sb,Te,Se) alloys: relationship between elaboration methods and applications

We will recall briefly the thermoelectric data on single crystals of Bi, Sb, Te, Se alloys grown by the travelling heater method. The crystalline quality of these single crystals will be characterized by X-ray topography (Synchrotron Beam). The observed dislocations are parallel to the cleavage planes with a density of 10/sup 5/ cm/sup -2/. Other defects in relationship with the growth are also observed. The composition homogeneity of the crystal is analysed by thermal probe. The quality of the single crystals permits us to perform experiments on diffusion. We recall the results for the anisotropic diffusion coefficient of selenium in bismuth telluride along the solidus line and we propose a mechanism of atomic diffusion. An important increase of the growth rate up to 40 mm per day gives materials with an excellent figure of merit (Zp=3.10/sup -3/ K/sup -1/, Zn=3.10/sup -1/ K/sup -1/).