Structural and transport properties of quenched and melt-spun BixSb2−xTe3 solid solutions (x = 0.40 and 0.48)

Abstract

We report on a detailed investigation of the structural and transport properties of BixSb2-xTe3 (x = 0.40 and 0.48) samples, prepared by either water quenching or melt-spinning (MS) and consolidated by spark plasma sintering (SPS), by means of X-ray diffraction, scanning and transmission electron microscopy, and transport property measurements (5-480 K). All the samples crystallize in the rhombohedral structure type of Bi2Te3. While the samples prepared by water quenching exhibit some segregations of the elements over the micron length scale, the MS samples are highly homogeneous. Unlike prior reports where an increase in the 2 dimensionless thermoelectric figure of merit ZT has been observed in MS samples, we find that both series of samples show similar peak ZT values. Owing to slight variations in the hole concentration, the maximum ZT is shifted closer to room temperature in MS samples with a peak ZT of 1.1 achieved at 340 K for x = 0.48. Our results highlight the extreme sensitivity of the ZT values to the Bi content and, for a given chemical composition, to slight variations in the hole concentration and microstructure. We further demonstrate the good reproducibility of the MS technique indicating that this method enables controlling the defect concentration inherent to these materials.

Многосекционные Термоэлементы, Преимущества И Проблемы Их Создания

“…В последние два десятилетия значительно выросла активность научных исследований в области термоэлектричества. Получены эффективные ТЭМ с параметром ZT , равным 1.2−1.4 [7][8][9][10][11][12]. Эти ТЭМ перекрывают практически весь рабочий интервал температур для термоэлектрических приборов от 150 до 1300 K. В настоящее время активно ведутся исследования с целью получения наноструктурированных ТЭМ.…”

Unraveling the Critical Role of Melt-Spinning Atmosphere in Enhancing the Thermoelectric Performance of p-Type Bi0.52Sb1.48Te3 Alloys

“…2 Nowadays, many novel compounds with earth-abundant elements or intrinsically low thermal conductivity have been designed as potential TE candidates. 3−6 Many of them are being explored for power generation applications, such as Bi 2 Te 3 , 7 GeTe, 8 PbTe, 9−11 and half-Heusler. 12 But, only Bi 2 Te 3 -based alloys have been commercialized for both waste heat recovery and electronic cooling.…”

“…The performance of TE materials is evaluated by the dimensionless figure of merit ZT = α 2 σT /κ, where α, σ, κ, and T are the Seebeck coefficient, electrical conductivity, thermal conductivity, and absolute temperature, respectively . Nowadays, many novel compounds with earth-abundant elements or intrinsically low thermal conductivity have been designed as potential TE candidates. − Many of them are being explored for power generation applications, such as Bi 2 Te 3 , GeTe, PbTe, − and half-Heusler . But, only Bi 2 Te 3 -based alloys have been commercialized for both waste heat recovery and electronic cooling.…”

“…The melt-spinning technique has long been utilized to produce amorphous metallic materials and continuous polymer ribbons with various physical properties, due to its capacity of producing abundant nanograins, and amorphous structures, originating from the rapid cooling rate of up to 10 4 –10 7 K/s. − The pioneering work on (Bi,Sb) 2 (Te,Se) 3 related binary alloys prepared through melt spinning or rapid quenching can be dated back to the 1980s and 1990s. − This motivates the subsequent researches of utilizing melt spinning to achieve high-performance thermoelectric materials, such as (Bi,Sb) 2 (Te,Se) 3 , ,− SnTe, − skutterudites, , Si–Mg 2 Si composites, GeTe-based materials, and SiGe alloys . Recently, Bi 2 Te 3 -based materials prepared by melt spinning followed by a consolidation process demonstrate improved ZT values in the range 1.1–1.5 compared to the corresponding ZM ingots. ,,, It should be noted that the MS process involves a series of variables, including nozzle diameter, copper wheel speed, injection gas pressure, impingement angle, ambient atmosphere, and ambient gas pressure, which have significant impact on the morphologies, compositions, and properties of resultant ribbons .…”

Enhanced Thermoelectric Performance of Bi0.46Sb1.54Te3 Nanostructured with CdTe

“…In addition to regulating the defects in the structure to improve thermoelectric properties, another scheme toward high-performance thermoelectric materials is through formation of nanostructures to scatter a wide range of phonon frequency and decrease the lattice thermal conductivity. ,− For example, in situ formation of nanostructures and grain size refinement can be achieved by melt-spinning in Bi 2 Te 3 -based alloys. − Melt-spinning process can effectively refine grain size because of its high cooling rate, which dramatically enhances phonon scattering, producing a lower lattice thermal conductivity.…”