Computational and experimental analysis on Te-doped ZnSb thermoelectric material

Abstract

In this study we report a combined theoretical and experimental work on the tellurium doping of thermoelectric ZnSb. We investigated the influence of tellurium on the phase's stabilities by density functional theory (DFT) calculations. During experimental validation by means of SEM and EPMA characterization "needlelike" areas of Te-doped ZnSb were identified. The experimental results also highlight that for the compositions Zn 0.5 Sb 0.5-x Te x (x=0.001, 0.05, 0.1) the system reaches a non-equilibrium state where ZnSb, ZnTe and Te-doped ZnSb are simultaneously present. The determination of the doping mechanism has demonstrated the formation of Te-doped Zn 4 Sb 3 after quenching, leading to the formation of Te-doped ZnSb due to the zinc diffusion during annealing. Presumed from experimental observation oxygen prevents the tellurium diffusion, which was confirmed by DFT calculations. These results lead to the conclusion of an inert processing chain as a necessary prerequisite for production of n-type ZnSb, which puts hurdles on a cheap and easily scalable tellurium doping for homogeneous and competitive products.

Fully Ab-Initio Determination of the Thermoelectric Properties of Half-Heusler NiTiSn: Crucial Role of Interstitial Ni Defects

“…This method is simple, but it does not take into consideration the phases which are in equilibrium with the compound containing defects [ 4 , 29 ]. To correct this, two methodologies can be used.…”

“…To avoid the limitations of the two previous formalisms, it is possible to modify Equation (4) by replacing the Δ f E(pure) by the Δ f E(multi) as suggested in our previous works [ 4 , 29 ]. In this third formalism, we assume that the defect will change the global composition of the alloy.…”

Unexpected band gap increase in the Fe2VAl Heusler compound

“…For thermoelectric applications, the full Heusler Fe2VAl compound may be a good challenger to conventional bismuth telluride (Bi2Te3) currently used in commercialized thermoelectric refrigerators. Most of the thermoelectric materials are small-gap semiconductors doped to obtain optimal carrier concentrations (around 10 19 charges.cm -3 ) which generally allow to have materials with a high figure-of-merit (named ZT = S 2 σT/ where T is the temperature, S the Seebeck coefficient, σ and  the electrical and thermal conductivity respectively). Fe2VAl exhibits a ZT max around 0.3 at 500K for Tantalum-doped bulk materials [1].…”

“…below the L21/B2 transition temperature (1353K)), partial disorder is observed due to inversions between Al and V atoms. In the spirit of our previous works on point defects in thermoelectric materials such as NiTiSn [14][15][16], NiHfSn [17], NiZrSn [18] and ZnSb [19][20], we here investigate the impact of temperature and partial disorder in the stoichiometric Fe2VAl through first-principles DFT calculations. The effect of off-stoichiometric defects has been discussed in a previous work [11].…”

Two-dimensional Mo1−xB2 with ordered metal vacancies obtained for advanced thermoelectric applications based on first-principles calculations

“…We used the same calculation method as Zhao et al 50 to obtain a maximum ZT value of 1.6 for SnS 0.91 Se 0.09 , and analyzed it experimentally. Pothin et al 51 analyzed Te-doped ZnSb materials with a computational method, and demonstrated the rationality of the calculated results through experiment. S. Sharma et al 52 verified the excellent thermoelectric performance of Bi 2 Te 3 material through theoretical calculation, and later Wang et al 53 successfully verified the excellent thermoelectric performance of the Bi 2 Te 3 material in experiments.…”