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Thermoelectric (TE) materials-based devices are valuable for translating heat into electricity, but the cost is largely driven by the use of purified metals required for efficient TE performance. This study focuses on tetrahedrite materials, which are cost-effective due to their abundance in copper ore mining waste and status as one of the most widespread sulfosalts on Earth. The research investigates the effects of co-doping and iso-valent doping on the TE properties of p-type tetrahedrite samples, specifically Cu 10 Mn 2 Sb 4 S 11 Se 2 (Sample A) and Cu 10 MnZnSb₄S 11 Se 2 (Sample B). These samples were synthesized using hot pressing at 773 K and compared with the existing pristine compound (Cu 10 Mn 2 Sb 4 S 13). Doping with Mn and Zn (1:1) at the Cu site was found to optimize carrier concentration and enhance phonon scattering, leading to an improved power factor. Additionally, the Se substitution at the S site also introduced band degeneracy, further increasing the power factor. Further, sample B exhibited the highest Seebeck coefficient (∼300 μV/K) at 650 K, in comparison to Sample A (∼225 μV/K) and the pristine compound (∼250 μV/K). On the other hand, Sample A demonstrated significantly higher electrical conductivity (∼0.76 × 10⁴ S/m at 650 K), ∿ three times greater than that of the other prepared samples. Notably, the power factor of Sample A (∼0.389 mW/mK2 at 650 K) was more than twice that of Sample B (∼0.141 mW/mK2) and the pristine compound (∼0.160 mW/mK2). These findings suggest that dual-site substitution at the Cu and S positions presents a promising strategy to augment the TE performance of tetrahedrite compounds. [Display omitted] • The p-type tetrahedrites compounds sample-A (Cu 10 Mn 2 Sb 4 S 11 Se 2) and sample-B (Cu 10 MnZnSb4S 11 Se 2) were successfully synthesized employing a hot press at 773K. • Doping at the Cu site with a 1:1 ratio of Mn and Zn optimizes carrier concentration and enhances phonon scattering, resulting in an improved power factor. • Se substitution at the S site introduced band degeneracy, further increasing the power factor. • Notably, the power factor of Sample A (∼0.39 mW/mK2 at 650 K) was more than twice that of Sample B (∼0.14 mW/mK2). [ABSTRACT FROM AUTHOR]

Thermoelectric (TE) materials-based devices are useful in converting heat into electricity. The cost of thermoelectric materials is mainly incurred from the purified pure metals used to make the efficient TE device. In the current study, tetrahedrite materials are considered due to their low cost, as these materials are abundant in mining waste of copper ores and also the most extensive sulfosalt on earth. Hence, to add value addition to mine waste materials, the composite approach has been employed to integrate the natural tetrahedrite (mine waste/tailings product) materials with synthetically developed tetrahedrite materials in the lab for the current investigation. Further, the optimum quantity of mine waste addition is optimized by the systematic investigation of TE performance with varying the mine waste percentage addition to the synthetic tetrahedrite. The p-type synthetic Cu 10 FeZnSb 4 S 13 (Sample-A) tetrahedrite compound and 70 (Cu 10 FeZnSb 4 S 13) + 30 (natural/mine waste) (Sample-B) have been synthesized employing hot-press at 773 K along with the pristine (Cu 10 Fe 2 Sb 4 S 13) tetrahedrite compound. Moreover, the Seebeck coefficient is increased by 36 % (220 μV/K to 300 μV/K) for Sample-B, as compared to sample A and it is ∿ 2 times higher as compared to the pristine compound. The power factor is increased by ∿ 3 times that of the Sample-A (0.05 mW/mK2 to 0.15 mW/mK2). In addition, the thermal conductivity of Sample-B compound was further reduced by 30 % than Sample-A (0.98 W/mK to 0.69W/mK) and ∿ 44 % more than the pristine compound. Finally, the zT of Sample-B increased to almost 3 times than Sample-A (0.05–0.15). [Display omitted] • The p-type tetrahedrites compounds Sample-A (Cu 10 FeZnSb 4 S 13) and Sample-B [70 Cu 10 FeZnSb 4 S 13 + 30 (natural minerals/mine waste)] have been successfully synthesized employing hot press at 773 K. • Higher effective mass and energy filtering phenomena significantly enhanced the Seebeck coefficient of Sample-B by ∿36 % as compared to Sample-A. • The power factor of Sample-B has been increased by ∿ 3 times as that of Sample-A (0.05 mW/mK2 to 0.15 mW/mK2). • The zT of Sample-B tetrahedrites composite increased to ≈ 3 times of pristine Sample-A. [ABSTRACT FROM AUTHOR]

Tetrahedrites, due to their promising thermoelectric properties, are one of the materials being investigated for use in thermoelectric generators. One problem is the lack of n-type tetrahedrites, which would be beneficial for the design of tetrahedrite thermoelectric modules. Preliminary theoretical studies have shown that elements from groups I and II can be introduced into the structural voids of tetrahedrite, acting as donor dopants, and should enable n-type conductivity. Therefore, in this work, an attempt was made to obtain and study magnesium-doped tetrahedrites. A series of samples, MgxCu12Sb4S13, with different magnesium contents were obtained and their phase and chemical compositions were characterized. It was observed that the structural changes occurring upon doping indicate that Mg atoms are likely to be embedded in the structural voids. The experimental studies have been supported by electronic structure calculations indicating that the most likely location of Mg is in the structural voids at the 6b Wyckoff position. Seebeck coefficient and resistivity measurements showed that doping with Mg reduces the concentration of holes, which is consistent with the predicted donor character of the dopant. However, the introduction of magnesium in sufficient amounts to achieve n-type conductivity was not successful. [ABSTRACT FROM AUTHOR]

Most of the energy produced is lost, mainly as waste heat. Thermoelectricity, which can directly convert heat into electricity, is seen with huge potential to recover part of such heat. However, to be widely used, it is necessary to be based on cheap, available, non-toxic, stable and easy-to-produce good thermoelectric materials. Here we present an overview of the potential of Cu–S based synthetic minerals for thermoelectric applications. In particular, we focus on tetrahedrites, which are world spread minerals with Cu10M2Sb4Si3 (M = Cu, Mn, Fe, Co, Ni, Zn) general formula that show high potential for thermoelectrics. An overview of their properties are presented, with emphasis on those relevant for thermoelectric applications. [ABSTRACT FROM AUTHOR]

Optimization and analysis of novel thermoelectric module is proposed in this research paper. The simulation for four thermoelectric modules were performed in COMSOL Multiphysics 5.4 software and detailed analysis of these thermoelectric modules were carried out. The three thermoelectric modules showed the efficiency and power output above-average thermoelectric modules. It also indicated that lead telluride based thermoelectric modules could be used in isolated areas due to toxicity of lead whereas tetrahedrite based thermoelectric module could be used in non-isolated areas due to its non-toxic properties. The proposed thermoelectric modules can be utilized in applications such as industries, deep space explorations, automobiles, thermal power plants, renewable electricity generation, hybrid renewable systems, etc. in an economically viable manner. [ABSTRACT FROM AUTHOR]

A Cu 12 Sb 3.6 Bi 0.4 S 10 Se 3 glass was prepared by melt spinning and crystallized by heat treatments at selected temperatures, the total preparation procedure taking less than one day. The sample characterization by powder X-ray diffraction, scanning and transmission electron microscopy complemented with EDS indicate the formation of compact materials, with a tetrahedrite relative weight fraction higher than 90% when treated at temperatures close to the crystallization peaks (∼200° C). Selenium enters the tetrahedrite structure, while bismuth precipitates in submicron and nanosized spherical shape phases depleted in copper and enriched in antimony, sulfur and selenium (when compared with the matrix composition). The characterization of electrical transport properties (electrical resistivity and Seebeck coefficient) indicate a behavior similar to that obtained by other methods on Cu 12 Sb 4 S 13 , with a maximum power factor of ∼400 μW/K 2 m at room temperature. [ABSTRACT FROM AUTHOR]

Computational inverse design and consequent experimental results allow for the identification of new tetrahedrite-mineral compositions as promising absorber candidates in drift-based thin-film solar cells. In device simulations, cell efficiencies above 20% are modeled with absorber layers as thin as 250 nm. These new compositions thus open opportunities for realization of a new class of high-efficiency thin-film solar cell. [ABSTRACT FROM AUTHOR]

• CdI 2 and LiI as fluxes were used for synthesis-growth of tetrahedrite crystals. • Cu 10-x Li x Cd 2 Sb 4 S 13 solid solution formed if LiI as flux was used. • PL bands with maxima at 1.08 eV (CdI 2 -flux) and at 1.16 eV (LiI-flux) were measured. • The thermal quenching E A of PL bands were 88±6 (CdI 2 -flux) and 199±7 meV (LiI-flux). • V oc = 506 mV, j sc = 4.46 mA/cm2, FF = 50%, η = 1.13% - with tetrahedrite grown in LiI. Synthesis of Cd-substituted tetrahedrite Cu 10 Cd 2 Sb 4 S 13 (TH Cd) monograin powders are performed by the molten salt synthesis-growth method using two different fluxes: CdI 2 and LiI. The X-ray diffraction (XRD) data of the materials indicates that mainly single phase of tetrahedrite Cu 10 Cd 2 Sb 4 S 13 compound is formed in both flux salts. XRD pattern of TH Cd crystals grown in LiI reveals a shift of all diffraction peaks, lower CdS content and a smaller lattice parameter values in comparison with those formed in CdI 2. Energy dispersive X-ray spectroscopy reveals stoichiometric composition of Cu 10 Cd 2 Sb 4 S 13 crystals grown in CdI 2 and Cu-poor grown in LiI. Analysis by Atomic Absorption Spectroscopy confirms the incorporation of Li into TH Cd crystals at the level of 6.7 × 1020 at/cm3. The photoluminescence (PL) study of Cu 10 Cd 2 Sb 4 S 13 microcrystals at T = 10 K shows single broad asymmetric photoluminescence bands with the maxima at around 1.08 and 1.16 eV for materials grown respectively in CdI 2 and LiI. The thermal quenching activation energy of this PL band is E A = 88±6 and 199±7 meV for TH Cd crystals grown in CdI 2 and LiI, respectively. Changes in the lattice parameters, composition and shift in PL maximum give evidences of Li incorporation from LiI into the crystal lattice of TH Cd forming Cu 10-x Li x Cd 2 Sb 4 S 13 solid solution. [ABSTRACT FROM AUTHOR]

This contribution deals with the mechanochemical synthesis, characterization, and thermoelectric properties of tetrahedrite-based materials, Cu12-xMxSb4S13 (M = Fe2+, Zn2+, Cd2+; x = 0, 1.5, 2). High-energy mechanical milling allows obtaining pristine and substituted tetrahedrites, after short milling under ambient conditions, of stoichiometric mixtures of the corresponding commercially available binary sulfides, i.e., Cu2S, CuS, Sb2S3, and MS (M = Fe2+, Zn2+, Cd2+). All the target materials but those containing Cd were obtained as single-phase products; some admixture of a hydrated cadmium sulfate was also identified by XRD as a by-product when synthesizing Cu10Cd2Sb4S13. The as-obtained products were thermally stable when firing in argon up to a temperature of 350–400 °C. Overall, the substitution of Cu(II) by Fe(II), Zn(II), or Cd(II) reduces tetrahedrites' thermal and electrical conductivities but increases the Seebeck coefficient. Unfortunately, the values of the thermoelectric figure of merit obtained in this study are in general lower than those found in the literature for similar samples obtained by other powder processing methods; slight compositional changes, undetected secondary phases, and/or deficient sintering might account for some of these discrepancies. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel affordable n-silicide/p-tetrahedrite thermoelectric module concept proposed. • Detailed validated multiphysics analysis done, TEG geometry optimization performed. • Pairs with optimal geometry preliminarily manufactured, assembled, characterized. • Power density/efficiency predictions: up to 5 kW/m2/5% (temperatures up to 620 K). • Affordable, non-toxic, performing generators enable viable industrial heat recovery. Thermoelectric (TE) generators allow the direct conversion of heat into electricity without moving parts and with little maintenance needs if carefully designed. However, their high cost per unit power produced has prevented their widespread use in waste heat recovery applications. The use of earth-abundant, affordable, non-toxic and performant TE materials such as n-silicide and p-tetrahedrite for TE generators is assessed in the present analysis. A full multiphysics model was used to optimize the geometry of an n-p TE pair/module using these materials and assess its performance. The approach taken implemented the matched load condition automatically and a broad range of conditions was tested and discussed. Several pairs with the optimal geometry were preliminarily manufactured, assembled and characterized. The experimental results were compared against the predictions, allowing to validate the multiphysics model. Power densities up to 5 kW/m2 were predicted for temperatures between 290 K and 620 K, with efficiencies up to 5%. If modules with such performance could be manufactured with electric contact resistances comparable to those found in currently available commercial modules, then a door to the viable recovery of waste heat in industrial and automotive applications could be opened. [ABSTRACT FROM AUTHOR]