Brittle thermoelectric semiconductors extrusion under high hydrostatic pressure

Abstract

Origins of strength increase of brittle materials like thermoelectric (TE) semiconductors during plastic deformation under high external pressure are analyzed. TE material stressed state in the process of extrusion is reviewed. Plastic deformation of monocrystalline TE material billet produced by extrusion under sufficiently high external hydrostatic pressure is more uniform than under ordinary ambient pressure and can lead to crack free extruded TE material structure, crystallographic symmetry of which coincides with original billet one. Experimental device realized the scheme of extrusion under high hydrostatic pressure is described. Here extrusion are carrying out in compressed liquid medium. The developed device ensures the value of hydrostatic pressure up to 2 GPa and extrusion temperature interval 300–600 K. Properties of extruded Bi‐Sb and Bi‐Sb‐Te single crystals are also reviewed. Possible application of presented method of extrusion under high hydrostatic pressure to form TE branches with highly accurate cross section for miniature TE coolers or generators is discussed.