Thermoelectric Properties of Solid Solutions Based on SnTe‐A^IITe‐Type Tin Telluride

Abstract

In recent years a number of papers has been devoted to studies concerning solid solution systems, mainly the substitutions of components on the basis of tin and germanium tellurides within the region close to them in composition. Such interest in these systepls has been aroused both by the physical properties of the above tellurides, in particular those of tin telluride (1 to 4) and by the possibility of using the compositions of solid solutions based on them, in various thermoelectric converters.The main purpose of this investigation is to study the effect of partial substitution of tin by the second-group elements on the thermoelectric properties of the SnTe--A Te-type solid solutions (where A = Zn, Cd, Hg) to make clear both the retention of the complex zonal structure and the defective behaviour of the crystal lattice peculiar to SnTe. I1There is only one piblication (5) dealing with studies on the solubility of CdTe in SnTe. We have studied the phase diagrams of SnTe-Zn (Cd, Hg)Te systems according to which the solubility of ZnTe in SnTe is of the order of 1.5 mol%, while that of CdTe amounts to 6 mol% and that of HgTe is 1.5 mol%.Specimens of appropriate geometry were prepared from ingots after annealing. the numerical value of electric conductivity being decreased with growing molecular weight of the component dissolved (Fig. 1).The dependence of the thermoelectromotive force (6) on the composition shows a weak minimum at a CdTe and HgTe content equal to 1 mol% and decreases continuously with growing concentration of ZnTe (Fig. 2).Just like the electric conductivity the total heat conductivity % drops with increasing per cent content of telluride A", the decrease in system being more substantial than that for the SnTe-Cd (I3g)Te system (Fig. 3).The concentration and mobility of current carriers calculated as p* = l/eRx and u = R d have extreme values at a 1 molg content of A Te in the composition range investigated (Fig. 4). In this case the concentration of current carriers which depends slightly on the composition shows a minimum, while the mobility of current carriers which according to its numerical values is more dependent on the composition displays a maximum. The results obtained in studying thermoelectric parameters may be explained on the basis of the double-valence-band model developed elsewhere (1 to 3, 6, 7) for de and Sn tellurides (it is retained in the solid solution region under study) and by the defective nature of the crystal lattice of the solid solution. The apparent mobility of current carriers is maximum when the content of the second-group tellurides is 1 mol%. As the per cent content of the

Extraordinary role of Hg in enhancing the thermoelectric performance of p-type SnTe

“…1(d), probably due to alloy scattering, and higher effective mass of holes caused by band structure modication, which we will discuss later. Collectively, both the lattice parameter and hole density variations suggest that the solubility limit of HgTe in Sn 0.98 Bi 0.02 Te is between 2% and 3%, which is higher than the $1.5 mol% observed by Nasirov et al 45 Electrical transport properties Contrary to the behavior of the electrical conductivity, the room temperature Seebeck coefficient increases prominently with increasing amounts of HgTe, from $22.1 mV K À1 for Sn 0.98 Bi 0.02 Te to $66.8 mV K À1 for the sample with 4%HgTe despite the gradually increased hole density, Fig. 2(c).…”

High thermoelectric performance by resonant dopant indium in nanostructured SnTe

“…Lead chalcogenides and their alloys can be engineered to exhibit high ZTs; however, environmental concern regarding Pb prevents their deployment in large-scale applications (6)(7)(8)(9)(10). Tin telluride (SnTe), a lead-free IV-VI narrow band-gap semiconductor has not been considered favorably as a good thermoelectric material because of its low ZT due to the relatively low Seebeck coefficient and high electronic thermal conductivity caused by intrinsic Sn vacancies (11)(12)(13), although SnTe has been used to alloy with other tellurides for better TE properties (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26). Even though there has been no real success in achieving good TE properties of lead-free SnTe, the similarity between the electronic band structure of SnTe and that of PbTe and PbSe (27)(28)(29)(30)(31) suggests it has the potential to be a good TE material, especially given the two valence bands (light-hole and heavy-hole bands) that contribute to the hole density of states.…”

Band engineering and precipitation enhance thermoelectric performance of SnTe with Zn-doping

“…[27] Unfortunately, the experimental study on Zn-doped SnTe does not exhibit this. [28] Moreover, the underlying thermoelectric properties have not been clarified. Indisputably, it is urgent to systematically investigate the intrinsic thermoelectric feature of Zn-doped SnTe.…”