Microstructure and Thermoelectric Properties of Hot-Pressed p-Type Bi_0.5Sb_1.5Te₃ Alloys Prepared by Rapid Solidification Technique

Abstract

Rapidly solidified bismuth-telluride based alloy foil; fabricated using the single roller melt spinning method exhibits a fine microstructure with unidirectional crystals. Meanwhile, a hot-pressing process, using rapidly solidified foils, was used to prepare the consolidated samples. The fine microstructure of this alloy is extremely effective in decreasing thermal conductivity because of the grain boundary scattering of the phonons, a key factor improving the thermoelectric properties of thermoelectric materials. Hot-pressed samples using these rapidly solidified foils display lower thermal conductivity values than the alloys made by the conventional hot-consolidating method using pulverized ingot powder. In this case, thermoelectric properties were investigated comparatively in terms of hot-pressed rapidly solidified foil specimens and pulverized powders of these foils under 53 mm in size, evaluating the dependence of the hot-pressing temperature and consequent pressure on the thermoelectric properties of these specimens. The maximum figure of merit (Z) obtained was 3:34 Â 10 À3 K À1 .

Formation of Supersaturated Solid Solutions Bi-Ag and Bi-Zn by Rapid Solidification Using Melt Spinning Technique

“…The semiconductors prepared by rapid solidification exhibit considerable improvements over alloys made from conventional materials. The thermoelectric materials fabricated by rapid solidification displayed a high figure of merit [1]. Formation of dendritic structure in thermoelectric alloys impairs its thermoelectric parameters [2]- [6].…”

Effect of Oxygen Content on Thermoelectric Properties of n-Type (Bi,Sb)<SUB>2</SUB>(Te,Se)<SUB>3</SUB> Alloys Prepared by Rapid Solidification and Hot-Pressing Techniques

“…2,3) The pulverization treatment of foils also affects the grain size, , and of the hot-pressed specimens. 2) In this study, it has become clear that the reduction of oxygen content by the heat-treatment process using hydrogen gas and the optimization of hot-pressing conditions are essential and effective means for obtaining a high figure of merit (Z).…”

“…The consolidated alloy has fine microstructure with a preferential crystal orientation and exhibits a higher value of figure of merit (Z). [1][2][3] As similar for SbI 3 , HgCl 2 and HgBr 2 , oxygen has an important role in the n-type alloys for the thermoelectric properties. 4,5) However, very little is known about the influence of oxygen element on the thermoelectric properties and carrier mobility of (Bi,Sb) 2 (Te,Se) 3 alloys.…”

“…In recent years, a new kind of thermoelectric materials with high performance has been prepared by a rapidly solidification technique. [1][2][3] The materials were prepared by hotpressing of melt-spun foils. The consolidated alloy has fine microstructure with a preferential crystal orientation and exhibits a higher value of figure of merit (Z).…”

Microstructure and Thermoelectric Properties of Hot-Pressed n-Type Bi<SUB>1.9</SUB>Sb<SUB>0.1</SUB>Te<SUB>2.6</SUB>Se<SUB>0.4</SUB> Alloys Prepared Using a Rapid Solidification Technique

“…5) We proposed a new rapid solidification process for fabricating new bismuthtellurides for thermoelectric use. 6,7) The rapid solidification technique can be expected to make lower in the direction parallel to the foil thickness rather than other directions. We previously reported that, in rapidly solidified foils fabricated using the single roller method, grains are formed with the c-plane perpendicular to the surface of the cooling roller during the solidification process.…”