Microstructure and thermoelectric properties of the medium-entropy block-textured BiSbTe1.5Se1.5 alloy

Abstract

Medium-entropy BiSbTe 1.5 Se 1.5 alloy has been prepared by self-propagating high-temperature synthesis (to prepare a starting powder with desired composition and structure) and spark plasma sintering (to prepare block-textured samples). Under texturing, a partial ordering of grains, which is typical for Bi 2 Te 3 -based alloys, takes place resulting in forming a lamellar grain structure. Lamellar sheets are not continuous for whole volume of the textured sample. There are blocks with continuous lamellar sheets of some definite orientation, but the orientations of the sheets in neighboring blocks are different from each other. Forming the block-textured structure can be related to specific features of the starting powder, applied to sinter the bulk samples. The starting powder was strongly inhomogeneous and particles in the starting powder were rather big and shape-isotropic. As result, the texturing can be initiated in local domains of volume independently from each other resulting in forming the blocks with different preferential grains orientation. Due to the block texturing, the thermoelectric properties of the BiSbTe 1.5 Se 1.5 alloy, measured perpendicularly or parallel to a texturing axis, are different. Many features, found in these properties, are typical for textured Bi 2 Te 3 -based alloys. The thermoelectric properties of the medium-entropy block-textured BiSbTe 1.5 Se 1.5 alloy can be believed to be promising enough. The highest thermoelectric figure-of-merit equal to ~0.43 was observed for the perpendicular measuring orientation. This alloy can be next applied as a precursor for developing five-or six-element high-entropy alloys with enhanced thermoelectric efficiency.

Preparation and characterization of nonstoichiometric Te-deficient and Te-rich thermoelectric Bi2-Gd Te3± compounds

“…As result, optimizing one property often degrades other properties. To decouple these thermoelectric properties, usually it is necessary in thermoelectric material to form defects of various nature [2][3][4][5][6][7][8][9][10]. At present, bismuth telluride, Bi 2 Te 3 , and Bi 2 Te 3 -based alloys with n-and p-types of conductivity are the best materials for low-temperature thermoelectric applications [11][12][13].…”

A Review on Doped/Composite Bismuth Chalcogenide Compounds for Thermoelectric Device Applications: Various Synthesis Techniques and Challenges

“…162 Further, a self-propagating high-temperature technique was Hence, there is a suppression in lattice thermal conductivity from 1.07 W/mK to 0.61 W/mK at 300 K, and a ZT of 0.67 at 473 K has been achieved for Bi 0.5 Sb 1.5 Te 3 . 163 Textured BiSbTe 1.5 Se 1.5 was prepared by Oleg et al 164 They achieved a maximum ZT of 0.43 at 500 K using self-propagation hightemperature technique. The texturing resulted in anisotropy in the specific electrical conductivity and thermal conductivity, as represented in Fig.…”

“…70 In some cases, the effective mass of a material results in higher valley degeneracy at a low-to near-room-temperature range. The significant contribution to carrier transport comes from the position of the Fermi level (E F ) from the conduction energy band (E C ) in an n-type semiconductor and the 164 valence energy band (E v ) in the case of a p-type semiconductor. Thermoelectric power increases with an increase in E C -E F , which helps increase weighted mobility and thermopower.…”

Thermoelectric properties of medium-entropy PbSbTeSe alloy prepared by reactive spark plasma sintering

“…Aim of this work is to prepare medium-entropy PbSbTeSe alloy by reactive spark plasma sintering (RSPS), which includes self-propagating high-temperature synthesis (SHS), and analyze features in thermoelectric properties of this alloy. Developing high-entropy (consisting of five or more principal elements in equimolar or near-equimolar ratio, which competes for the same position in crystal lattice) and medium-entropy (consisting of three or four principal elements) alloys is effective approach in modern materials science [1][2][3]. Due to effects of highmixing entropy and chemical complexity, these alloys show unique properties.…”