Grain size effects on thermoelectrical properties of sintered solid solutions based on Bi2Te3

Ionescu, Radu; Jaklovszky, J.; Nistor, N.; Chiculita, A.

doi:10.1002/pssa.2210270103

Cited by 58 publications

(28 citation statements)

References 6 publications

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“…31 The p H of the HD samples is systematically lower than that of the ZM samples because of the donor-like effect. 47,48 The non-basal slip during the deformation processing (typically upon HD) tends to create 3Te-2Bi vacancy-interstitial pairs, 49 and the Bi 0 Te will more readily diffuse back into the Bi sublattice sites; thus, excess Te vacancies and electrons are produced: 47…”

Section: Carrier Concentration and Electrical Propertiesmentioning

confidence: 99%

Attaining high mid-temperature performance in (Bi,Sb)2Te3 thermoelectric materials via synergistic optimization

Zhu

et al. 2016

NPG Asia Mater

132

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For decades, zone-melted Bi 2 Te 3 -based alloys have been the most widely used thermoelectric materials with an optimal operation regime near room temperature. However, the abundant waste heat in the mid-temperature range poses a challenge; namely, how and to what extent the service temperature of Bi 2 Te 3 -based alloys can be upshifted to the mid-temperature regime. We report herein a synergistic optimization procedure for Indium doping and hot deformation that combines intrinsic point defect engineering, band structure engineering and multiscale microstructuring. Indium doping modulated the intrinsic point defects, broadened the band gap and thus suppressed the detrimental bipolar effect in the mid-temperature regime; in addition, hot deformation treatment rendered a multiscale microstructure favorable for phonon scattering and the donor-like effect helped optimize the carrier concentration. As a result, a peak value of zT of~1.4 was attained at 500 K, with a state-of-the-art average zT av of~1.3 between 400 and 600 K in Bi 0.3 Sb 1.625 In 0.075 Te 3 . These results demonstrate the efficacy of the multiple synergies that can also be applied to optimize other thermoelectric materials. INTRODUCTIONThermoelectricity is the simplest technology for direct heat-toelectricity power generation. Thermoelectric (TE) devices are all solid state, without rotation parts or working fluids, and are thus easy to miniaturize. These modular characteristics make TE devices reliable, durable and easy to use in tandem with other energy conversion technologies. 1,2 The energy conversion efficiency of a TE device is primarily determined by the TE material's dimensionless figure of merit, defined as zT = α 2 σT/κ, where α is the Seebeck coefficient, σ is the electrical conductivity, κ is the total thermal conductivity (including the lattice contribution κ L and the carrier contribution κ e ) and T is the absolute temperature. 2 zT is generally a function of temperature whereas waste heat is the energy source for TE power generation. It is useful to compare the optimal operation temperature ('service temperature') of state-of-the-art TE materials and the temperature range in which most of the waste heat is produced. State-of-the-art TE materials have their best zT values (those between 1 and 2) in different temperature regimes; for example, Bi 2 Te 3 works best near room temperature, 3,4 whereas PbTe, Mg 2 Si 1-x Sn x , Half-Heusler compounds and filled skutterudites generally reach their best performance above 600 K. [5][6][7][8][9][10][11][12][13][14] There is a conspicuous lack of high-performance TE materials between 400 and 600 K, the

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Section: Carrier Concentration and Electrical Propertiesmentioning

confidence: 99%

Attaining high mid-temperature performance in (Bi,Sb)2Te3 thermoelectric materials via synergistic optimization

Zhu

et al. 2016

NPG Asia Mater

132

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“…As it is a well-known fact that the hole concentration is created by the antistructure defects generated by the occupation of Te sites with Bi and Sb atoms for the p-type Bi 2 Te 3 -Sb 2 Te 3 solid so- Table 1 Hole concentration (n), mobility (µ) of samples (the applied magnetic field is perpendicular to the crystal growth direction for the zone-melted ingot and parallel to the pressing direction for the sintered samples) lutions, which can be described as: Bi 2 Te 3 = 2Bi Te + 2V Bi + V Te + (3/2)Te 2(g) + 2h; Sb 2 Te 3 = 2Sb Te + 2V sb + V Te + (3/2)Te 2(g) + 2h, where V Te is Te vacancy, V × Bi(Sb) is Bi(Sb) vacancy [15]. Ionescu et al [16] reported that through mechanical treatment, more Te vacancies than Bi(Sb) vacancies are generated mainly due to the nonbasal slip which gives on the average, 3 Te to 2 Bi vacancy-interstitial pairs. Navratil et al [17] proposed an interaction of such vacancies with the antistructure defects, as: 2V Bi(Sb) + 3V Te + Bi(Sb) Te = V Bi(Sb) + Bi(Sb) × Bi(Sb) + 4V Te + 3e , where e is the produced electron, which consequently decreases the hole concentration.…”

Section: Resultsmentioning

confidence: 98%

Thermoelectric performance of p-type Bi–Sb–Te materials prepared by spark plasma sintering

Jiang

Chen

Bai

et al. 2005

Journal of Alloys and Compounds

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“…In particular, the fact that p-type stoichiometric Bi2Te3 samples will become n-type when subjected to heavy plastic deformation has been explained via an excess formation of VTe over VBi''' [10,50,51]. Vacancies distort the lattice more strongly than antisites, since their coulombic repulsion is twice (for VTe) or three-times (for VBi''') that of an antisite.…”

Section: Microstrain and Lattice Parameter Changementioning

confidence: 99%

Anomalous grain refinement trends during mechanical milling of Bi2Te3

Humphry-Baker

Schuh

2014

Acta Materialia

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Abstract:The structural evolution of nanocrystalline Bismuth Telluride (Bi2Te3) during mechanical milling is investigated under different milling energies and temperatures.After prolonged milling, the compound evolves toward a steady-state nanostructure that is found to be unusually strongly dependent on the processing conditions. In contrast to most literature on mechanical milling, in Bi2Te3 we find that the smallest steady-state grain sizes are attained under the lowest energy milling conditions. An analysis based on the balance between refinement and recovery in the steady state shows that two regimes of behavior are expected based on the thermo-physical properties of the milled powder. Bi2Te3 lies in a relatively unusual regime where greater impact energy promotes adiabatic heating and recovery more than it does defect accumulation; hence more intense milling leads to larger steady-state grain sizes. Implications for other materials are discussed with reference to a "milling intensity map" that delineates the set of material properties for which this behavior will be observed.

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Grain size effects on thermoelectrical properties of sintered solid solutions based on Bi2Te3

Cited by 58 publications

References 6 publications

Attaining high mid-temperature performance in (Bi,Sb)2Te3 thermoelectric materials via synergistic optimization

Attaining high mid-temperature performance in (Bi,Sb)2Te3 thermoelectric materials via synergistic optimization

Thermoelectric performance of p-type Bi–Sb–Te materials prepared by spark plasma sintering

Anomalous grain refinement trends during mechanical milling of Bi2Te3

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