Structural and Thermoelectric Properties of Nanostructured Nominally Stoichiometric Pb1−x Bi x Te Prepared by Mechanical Alloying

Abstract

In this work we investigate the influence of bismuth substituted for lead in lead telluride. The material was nanostructured by mechanical alloying (MA) and was compacted via short term sintering (STS) and, alternatively, hot pressing (HP). Syntheses of samples with substitution up to 6 at.-% of bismuth were carried out twice to ensure reproducibility. All relevant thermoelectric transport parameters were measured in a wide temperature range from 123 K and 173 K, respectively, to 773 K. Two different techniques for measuring the electrical conductivity and the Seebeck coefficient were used, one at low and the other at high temperature. A higher bismuth content of 4 at.-% to 6 at.-% was found to lead to best thermoelectric properties with a maximum ZT value of about 0.7 at 723 K for 4.0 at.-% bismuth. The structure was examined in detail via X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM). A key feature of the microstructure is the inhomogeneous distribution of bismuth in the lead telluride matrix and the occurrence of bismuth-rich regions on the nanoscale related to a remarkable increased carrier concentration and mobility.

Improved electrical conductivity and power factor in Sn and Se co-doped melt-grown Bi2Te3 single crystal

“…The two additional reflections noticed around the plane (015) are due to the unveiling of twining orientations [19,20]. A systematic decrease in the crystallite size has been found with decreasing lattice parameters (Table 1), which is reported to be because of Sn atoms non-intercalation through Van der Waals interlayer [21]. The crystallite size is determined using the Williamson-Hall formula [16].…”

Effect of Heating Rate on Bulk Density and Microstructure in Bi2Te2.7Se0.3 Sintering

“…This secondary phase could be caused by tellurium volatilization, as reported by Falkenbach et al, and the same peak can be observed in Joint Committee on Powder Diffraction Standards (JCPDS) PDF 15-0820. 14 Figure 6 shows a graph of the bulk density of the Bi 2 Te 2.7 Se 0.3 pellet according to the heating rate during rapid sintering. The Bi 2 Te 2.7 Se 0.3 pellets showed a density of about 5.52 g/cm 3 when sintered at 570°C for 10 min at heating rate of 10°C/min, conditions commonly used in pressureless sintering.…”

Colossal variations in the thermopower and n–p conductivity switching in topological tellurides under pressure

“…1(c)]. 114 Under applied high pressure above 5.5-7 GPa, this phase undergoes a phase transition to an orthorhombically distorted structure of Pnma symmetry. [56][57][58][59]115,116 Although this transition has been discovered a long time ago, 76,117-122 and high-pressure effects on the electronic band structure of PbTe and its parameters were investigated in a plenty of studies, 48,49,51,53,54,63,64,[123][124][125][126] the pressure-driven reconstructions of the band structure of PbTe in both the NaCl and Pnma phases remain obscure to the date.…”