Thermoelectric properties of p-type (Bi2Te3)x(Sb2Te3)1−x single crystals doped with 3 wt. % Te

Abstract

In the present work, thermoelectric properties of p-type (Bi2Te3)x (Sb2Te3)1−x single crystals doped with 3 wt. % Te are theoretically explored for various chemical compositions (x = 0.18, 0.19, 0.20, 0.22, 0.24, 0.26) in the temperature range of 290–500 K. The influence of the chemical composition in enhancing the thermoelectric figure of merit (ZT) is discussed in detail. Using the nearly-free electron approximation and the Fermi-Dirac statistics, the temperature dependences of Fermi level (Ef), Seebeck coefficient (S), and electrical conductivity (σ) are successfully reproduced as reported in the experimental study of Li et al. [Intermetallics 19, 2002 (2011)]. The thermal conductivity contributions from phonons (κph), acceptor holes (κh), and electron-hole pairs (κbp) are included by employing Srivastava's scheme, Wiedemann-Franz law, and Price's theory, respectively. By combining all three contributions of the thermal conductivity we successfully explain the experimental measurements of the total thermal conductivity as reported by Li et al. Furthermore, it is theoretically found that among all the compositions the p-type 20%(Bi2Te3)-80%(Sb2Te3) sample has the maximum ZT value of 1.31 at 390 K, which is also in good agreement with the experimental results obtained by Li et al.

Tuning phonon properties in thermoelectric materials

“…The results for the temperature dependence of the Fermi energy, Seebeck coefficient, electrical resistivity and total thermal conductivity in p-type (Bi 2 Te 3 ) x (Sb 2 Te 3 ) 1−x single crystals doped with 3 wt% Te are shown in figures 31 and 32. The theoretical modelling [168] successfully reproduces the measured results presented in [169]. The differences in the thermal conductivity results below 350 K for different values of the alloy concentration parameter x can be easily understood to arise from the alloy scattering of phonons.…”

“…(a) For the n-type quantum well of width d A = 7 nm the maximum value of the power factor is an order of magnitude larger than its bulk value given in [166]. The highest value of the power factor for the p-type quantum well sample with d A = 10 nm is nearly four times bigger than its bulk value obtained in [168]. (b) An order of magnitude smaller values of κ ph are predicted for almost all the considered quantum well systems compared to their bulk forms.…”

“…The highest ZT value is experimentally obtained for the p-type 20% Bi 2 Te 3 -80% Sb 2 Te 3 sample as 1.33 at 398 K. Theoretically it is found [168] that the x = 0.20 sample has the largest ZT as 1.31 at 390 K, which is in very good agreement with the experimental value [169]. The reason that the x = 0.20 sample has the biggest value of ZT among the six compositions is two-fold: it has the lowest total thermal conductivity and has one of the highest power factor values.…”

Polymer-mixed Sb2Te3/Te nanocomposites exhibiting p-type to n-type conduction reversal and thermal conductivity reduction

“…To improve the TE efficiency of Sb 2 Te 3 several efforts have been made like the formation of nanocomposite [16][17][18][19][20][21][22][23], doping [15], orientation engineering [24], and nanostructuring [25,26]. The formation of nanocomposite has got much attention due to its advantage in reducing thermal conductivity while maintaining a high value of power factor (PF = S 2 σ) [27,28].…”

Low-temperature Minimum in the Electrical Resistivity of the Bi1.9Lu0.1Te3

“…It should be noted that rare earth dopants can sufficiently effect on the electrical properties of the Bi2Te3 semiconductor via changes of the concentration and mobility of charge carries. A few mechanisms like the Kondo effect [6], an electron scattering by neutral or ionized impurity atoms [7], a hopping conductivity [8,9] can control the electrical properties of the doped Bi2Te3. All of these mechanisms are effective for lowtemperature range.…”