Thermal Properties for Hot-Pressed n-type (Bi_1-xSb_x)₂Te₃ Alloys

Abstract

We have measured the thermal properties of an n-type hot-pressed Bi1.8Sb0.2Te3 alloy with a carrier concentration of 3.1×1019 cm-3. With the adjustable parameters determined from these experimental data, the dependence of thermal properties on the carrier concentrations is investigated, using the two-band-conduction model with a mixed scattering mechanism and a small fluctuation theory. The maximum dimensionless figures of merit of the alloy in a carrier concentration range of 0.8–3×1019 cm-3 have values over 0.7 at temperatures between 250 K and 300 K and a minimum thermal conductivity of 1 W/Km. These alloys are comparable to single crystals, showing the possibility that they provide higher thermoelectric performance than the single crystals, since their microstructure can be controlled by hot-press processing.

Significant Enhancement in the Thermoelectric Performance of a Bismuth Telluride Nanocompound through Brief Fabrication Procedures

“…The Seebeck coefficient increased due to the decrease in the carrier density, but it might be still low for thermoelectric applications − the Seebeck coefficient is quite lower than that of other Bi 2 Te 3 . 42,43 Because a BiTe-type thermoelectric material is known to show optimized thermoelectric properties when a carrier density ranges from 1 × 10 18 to 1 × 10 19 cm −3 , 44,45 we expect that the carrier density after the thermal treatment (6.53 × 10 19 cm −3 , Table 1) should be even lower.…”

Enhancement of Thermoelectric Figure‐of‐Merit by a Bulk Nanostructuring Approach

“…Using the ball‐milling and hot‐pressing method, other groups also prepared p‐type Bi x Sb 2−x Te 3 nanocomposites27, 32, 101, 131–135 and p‐type (Bi,Sb) 2 (Te,Se) 3 nanocomposites 102 . ZT is less than 1.0 and lower than that of the crystalline ingots.…”

Effects of crystal-alignment and grain shape on the thermoelectric properties of Bi0.5Sb1.5Te3 alloys

“…The prepared materials have grain boundaries and anisotropy due to their alignment. To improve the thermoelectric performance, the thermoelectric properties were extensively investigated by controlling the grain size [4], carrier concentration [5][6][7] and the crystal alignment [8][9][10], which can be controlled by using the spark plasma sintering (SPS) method with magnetic fields of different strengths. The alloys prepared by the SPS method have a mixed system containing the polycrystalline and powder phases.…”

“…We define polycrystalline and powder phases as follows: the polycrystalline phase has grains in which the c-axis of the crystallites lies randomly in a plane perpendicular to the growth direction, and the powder has grains in which the c-axis is completely randomly oriented. The thermoelectric properties of both materials were theoretically investigated [6,11].…”