Microstructural study of Bi2Te3 material obtained by ultrarapid quenching process route

Structural and Electrical Properties Characterization of Sb1.52Bi0.48Te3.0 Melt-Spun Ribbons

“…As the XRD pattern of the free surface is similar to that of ground ribbons, the level of texturing should be limited to a region close to the contact surface. Our results are however quite different from those obtained by Koukarenko et al [46], who studied in detail the texture formation in Bi2Te3 ribbons. Their investigation revealed a well-defined (025) texture independent of the quenching temperature, the ribbon thickness and the heat treatment.…”

“…In these prior investigations, the melt-spinning technique was shown to produce homogeneous ribbons with identical electrical properties although the intrinsic properties of the carriers (concentration and mobility) are different from those of the bulk SPS samples. The excellent reproducibility of the transport properties in Bi 0.48 Sb 1.52 Te 3 ribbons observed herein thus confirms the conclusions drawn for analogous compounds [43][44][45][46][47][48][49]60]. Finally, it should be kept in mind that the electronic properties of mixed crystals based on Sb 2 Te 3 -Bi 2 Te 3 are governed by native defects, the influence of which outweighs the role of differences in the microstructure of the samples.…”

“…Further investigations on the Bi 2−x Sb x Te 3 (0 ≤ x ≤ 1) system by the same authors showed that substituting Sb for Bi tends to lessen the (025) texture and favors the appearance of the (110) texture [48]. The difference between the textures observed in [46] and in our case could be linked to different cooling rates since the thickness of the ribbons obtained in their studies was significantly higher (between 20 and 35 µm). Figure 1 shows the XRD patterns collected on ground ribbons, as well as on the surface in contact with the copper wheel and the free surface.…”

“…The heat convection coefficient for a polished copper surface is estimated to be in the range of 1-2 × 10 5 W m −2 K −1 [53]. In the literature, the excessive temperature of the melt is defined as the difference between the temperature of the melt and the temperature of the wheel considered to be equal to room temperature [46]. For ribbons with a thicknesses close to 8 µm, the cooling rate is then estimated to be of the order of 10 6 K s −1 .…”

“…Because melt-spun ribbons are subsequently consolidated to obtain bulk dense specimens, a detailed investigation of their microstructure-properties relationships is essential to better understand the influence of the MS process on the thermoelectric properties of Bi 2 Te 3 -based materials. In this context, Koukharenko et al investigated the microstructure and transport properties of ribbons obtained from Bi 2 Te 3 and from the Bi 2−x Sb x Te and Bi 2−x Sb x Te 2 systems [44][45][46][47][48][49]. However, melt-spun ribbons in the ternary p-type Bi x Sb 2−x Te 3 solid solution (0.48 ≤ x ≤ 0.52) have received much less attention even though the best thermoelectric performances are achieved for these particular compositions [2].…”