Abstract
Cation substitutional doping is an effective approach to modifying the electronic and thermal transports in Bi2Te3-based thermoelectric alloys. Here we present a comprehensive analysis of the electrical and thermal conductivities of polycrystalline Pb-doped p-type bulk Bi0.48Sb1.52Te3. Pb doping significantly increased the electrical conductivity up to ~2700 S/cm at x = 0.02 in Bi0.48-xPbxSb1.52Te3 due to the increase in hole carrier concentration. Even though the total thermal conductivity increased as Pb was added, due to the increased hole carrier concentration, the thermal conductivity was reduced by 14–22% if the contribution of the increased hole carrier concentration was excluded. To further understand the origin of reduction in the thermal conductivity, we first estimated the contribution of bipolar conduction to thermal conductivity from a two-parabolic band model, which is an extension of the single parabolic band model. Thereafter, the contribution of additional point defect scattering caused by Pb substitution (Pb in the cation site) was analyzed using the Debye–Callaway model. We found that Pb doping significantly suppressed both the bipolar thermal conduction and lattice thermal conductivity simultaneously, while the bipolar contribution to the total thermal conductivity reduction increased at high temperatures. At Pb doping of x = 0.02, the bipolar thermal conductivity decreased by ~30% from 0.47 W/mK to 0.33 W/mK at 480 K, which accounts for 70% of the total reduction.
Highlights
The thermoelectric (TE) effect offers the direct conversion of a temperature gradient into electrical energy, and vice-versa
The electrical and thermal conductivities and Seebeck coefficient of a series of polycrystalline bulk Pb-doped p-type Bi0.48 Sb1.52 Te3 were comprehensively analyzed using the single parabolic band model and Debye–Callaway model, and compared with that of Bi0.48 Sb1.52 Te3 polycrystalline alloys to closely examine the effect of Pb substitution on bipolar conduction and lattice thermal conductivity
A two-band model based on the single parabolic band model showed that Pb doping effectively suppressed the bipolar thermal conduction
Summary
The thermoelectric (TE) effect offers the direct conversion of a temperature gradient into electrical energy, and vice-versa. It has been recently found that dense dislocations formed at grain boundaries can phonon by the additional scatteringscattering of mid-frequency phonons phonons [3]. Substitutional doping intensifyscattering phonon scattering by the additional of mid-frequency [3]. Substitutional isdoping another to reducing κ latt bythe introducing point defects for defects phononfor scattering, is effective another approach effective approach to the reducing κlatt by introducing point phonon which target high-frequency phonons. It has been experimentally found that certain elements, such as scattering, which target high-frequency phonons. The substitutional approach elements, suchAg, as Al, Cu, Ag, Fe, reduce κlattHowever, effectively. The TE transport properties, including S, σ, κκlatt and increase power factor latt and increase power factor (σ·S ) [9].
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