The effect of In doping on thermoelectric properties and phase transition of Zn₄Sb₃at low temperatures

Abstract

β-Zn4Sb3 is a promising thermoelectric material for energy conversion applications due to its exceptional low thermal conductivity. In this report, the effect of In substitution on thermoelectric properties and β to α/α′ phase transition of indium doped compounds (Zn1−xInx)4Sb3 (x = 0–0.02) were investigated at temperatures from 5 to 310 K. The results indicated that low-temperature (T < 300 K) thermal conductivity λ of the doped β-(Zn1−x Inx)4Sb3 (x ≠ 0) reduced remarkably as compared with that of Zn4Sb3 presumably due to enhanced impurity (dopant) scattering of phonons. Direct current electrical resistivity ρ and thermopower S were found to decrease and then increase moderately with the increase in the In content, which could be ascribed to the introduction of donors due to substitution of In3+ for Zn2+, leading to increased electron contribution. Moreover, it was found that the β to α/α′ phase transition of Zn4Sb3 was completely prohibited by In doping, implying that In was substituted predominantly for interstitial Zn and hindered their ordering. In addition, the thermoelectric figure of merit (=S2T/ρλ, where T is temperature) of the doped compound β-(Zn1−xInx)4Sb3 (x ≠ 0) was smaller than that of Zn4Sb3 at the low temperatures because of substantial decrease in their thermopower, suggesting that In substitution for Zn in Zn4Sb3 is not beneficial for raising its low-temperature thermoelectric properties.

Cd Substitution in MxZn4−-xSb3: Effect on Thermal Stability, Crystal Structure, Phase Transitions, and Thermoelectric Performance

“…Another interesting feature is that the DSC signal becomes smaller with increasing Cd content, which could indicate that Cd-doping has a suppressing effect on the phase transition. This effect has also been noted by other authors in studies where In, Ga and Sn were used as doping elements. − It has been speculated whether the effect could be explained by the dopant atom substituting on the interstitial Zn sites, because the low-temperature phase transitions are accompanied by ordering of interstitial sites, and substitution on these sites therefore could have a large effect on the phase transition . The relations are the same when heating the samples, e.g., the onset of the phase transition occurs at lower temperatures for the two samples with highest Cd content.…”

Crystal structure, electronic structure, and thermoelectric properties ofβ-Zn4Sb3from first principles

“…Doping is an effective approach to optimize the thermoelectric properties by adjusting the carrier concentration, 7 nevertheless it is found that doping in ␤-Zn 4 Sb 3 is not always beneficial. Liu et al 8,9 and Tsutsui et al 10 have investigated the effects of Al, Ga, and In doping on the thermoelectric properties of ␤-Zn 4 Sb 3 , respectively. They found that the substitutions increase both the electrical resistivity and the Seebeck coefficient resulting in a reduction in ZT at high doping levels.…”

Thermoelectric properties of hot-pressed Zn4Sb3−xTex

“…Nakamoto et al reported that Cd doping increased both the electrical resistivity and the Seebeck coefficient, and power factor reached a maximum when Cd content was 20% at 300 K [15]. Liu et al found In substitution lead to a remarkable reduction for thermal conductivity due to the enhanced impurity scattering on phonons [16]. Pedersen et al reported the thermal stability of Zn 4 Sb 3 doped with 2.5% tellurium; however, the influence of Te-doping on thermoelectric properties was not studied [17].In this paper, a series of samples with composition of Zn 4 Sb 3−x Te x (x = 0.02-0.08) were fabricated through vacuum melting method followed by hot-pressing in this study, and the influence of Te-doping on their thermoelectric properties has been investigated in detail.…”