Dysprosium-Doping Influence on the Microstructure and Texturing of Bismuth-Telluride Thermoelectric Materials

The preparation and identification of microstructure features as well as the texturing of the thermoelectric material Bi₂ Te_2.7 Se_0.3 doped with dysprosium are considered. The textured compounds Bi_2–x Dy_x Te_2.7 Se_0.3 with x = 0.0000; 0.0010; 0.0025; 0.0050; 0.0100, and 0.0200 were obtained by means of solvothermal synthesis of the original powders and their subsequent spark plasma sintering. Dysprosium doping effects several interrelated phenomena. The first one is particle size reduction of the original powder with increasing x. This effect is explained by an increase in the ionicity of the covalently polar bonds Bi(Dy)–Te with increasing Dy content on account of the difference in the electro-negativity of Bi and Dy. The second effect is associated with average grain size reduction with increasing x in bulk samples, which is determined by a corresponding change in the particle size in the original powder with different amounts of alloying. This phenomenon also effects greater texturing in the samples.