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

Abstract

N-type Bi 1:9 Sb 0:1 Te 2:6 Se 0:4 alloys were prepared by a rapid solidification technique and subsequent hot-pressing method. The microstructure and thermoelectric properties of the alloys were investigated as a function of the hot-pressing temperature and pressure. The X-ray diffraction measurements indicate that the grains are preferably aligned with the c-axis perpendicular to the direction of the hot-pressing force by the hot-pressing. Hot-pressing at higher temperature promotes the grain growth in the alloys. The Seebeck coefficient () and electrical resistivity () decrease with an increase in the hot-pressing temperature, whereas the thermal conductivity () increases. The specimens prepared at higher temperature greater than 733 K show better thermoelectric performance: the largest dimensionless figure of merit (ZT) is 1.08 at room temperature.

Thermoelectric Properties of Texture-Controlled Bi<SUB>1.9</SUB>Sb<SUB>0.1</SUB>Te<SUB>2.7</SUB>Se<SUB>0.3</SUB> Compounds Prepared by Angular Extrusion Technique

“…These were hot-pressed under a pressure of 100 MPa at 653 K in argon atmosphere in order to increase their density. Hot-pressing the rapidly solidified foil of bismuth telluride based compounds promotes grain growth at temperatures above 673 K. 11) To prevent grain growth from hot-pressing after angular extrusion, the hot-pressing was performed at 653 K which is the lowest possible angular extrusion temperature. Figure 1 shows a schematic diagram describing angular extrusion and hot pressing processes.…”

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).…”