Suppression of Interfacial Diffusion in Mg₃Sb₂ Thermoelectric Materials through an Mg_4.3Sb₃Ni/Mg_3.2Sb₂Y_0.05/Mg_4.3Sb₃Ni-Graded Structure

Abstract

The Zintl compound, n-type Mg3Sb2, has been extensively investigated as a promising thermoelectric material. However, performance degradation caused by the loss of Mg element during device preparation and service is a main disadvantage in its utilization in thermoelectric devices. To suppress volatilization, diffusion, or reaction of Mg, we designed a graded concentration junction to control the interfacial elemental diffusion and improve the stability of the thermoelectric joint. We utilized the reaction product at the Ni/Mg3.2Sb2Y0.05 interface, the phase Mg4.3Sb3Ni, as a barrier layer material, and prepared Mg4.3Sb3Ni/Mg3.2Sb2Y0.05/Mg4.3Sb3Ni junctions. The results show that the interface behavior of the thermoelectric junction is optimized by the gradation of elemental concentration, thermal expansion coefficient, and work function. The Mg4.3Sb3Ni/Mg3.2Sb2Y0.05/Mg4.3Sb3Ni single-leg device showed high thermal stability at 673 K for 20 days, the contact resistance was stable at around 10 μΩ cm2, and the shear strength was maintained at about 20 MPa. The conversion efficiency of its single-leg device maintains nearly 90% of the best performance after aging at 673 K for 20 days.

Interface and Surface Engineering Realized High Efficiency of 13% and Improved Thermal Stability in Mg3Sb1.5Bi0.5‐Based Thermoelectric Generation Devices

“…The raw testing data can be seen in Figure S4, Tables S1, S2, and S3, Supporting Information. In contrast, the k ρc and k σs in the reported literature [36,38,40] are over 37 µΩ cm 2 s 1/2 and 24 MPa s 1/2 , respectively, which are higher than our as-fabricated TEiM/TEcM interfaces, suggesting that the operating lifespan of FeCrTiMnMg/Mg 3 Sb 1.5 Bi 0.5 interfaces is significantly increased, which should be the most stable electrode contact interface in the reported Mg 3 Sb 2 -based TE devices.…”

“…Thus, it is difficult to balance the high σ s and low ρ c values of a single‐element TEiM. Some alloying TEiM layers for n‐type Mg 3 Sb 1‐ x Bi x TEcM legs, including 304 stainless steel (304SS), [ 36 ] Mg 2 Cu, [ 10 ] Fe 90 Sb 10 , [ 37 ] and Mg 3.4 Sb 3 Ni [ 38 ] were subsequently reported to show lower ρ c values. Very recently, Song et al reported that the NiFe/Mg 3 Bi 1.5 Sb 0.5 contact exhibits a highly stable ρ c of 13 µΩ cm 2 after aging for over 2100 h. [ 39 ] The authors have suggested an alloying approach to design the TEiM rather than using available alloys, which has already been verified as an effective technique route with some necessary characteristics, including high bonding propensity, coefficient of thermal expansion (CTE) matching, diffusion passivation, and dopant inactivation.…”

Role of Pb Doping on the Thermoelectric Properties of Mg3Sb1.8‐yBi0.2Pby Alloys

“…[7][8] Ideal thermoelectric materials not only should possess high thermoelectric performance, but also meet the requirements of non-toxic, good chemical stability, and thermal stability in practical applications. [9][10][11][12][13][14][15] Nowadays, many tellurides have been developed as state-of-the-art thermoelectric materials, such as Bi 2 Te 3 , PbTe, SnTe and GeTe-AgSbTe 2 . [16][17][18][19][20][21] However, these materials contain the common toxic and scarce tellurium, which serves as the main constraint for their large-scale applications.…”

“…To this end, Mg 3 Sb 2 -based compounds have attracted the interest of many researchers due to their abundant and nontoxic constituent elements, cost-effectiveness and advanced thermoelectric properties. [9,12,14,22,23] In particular, Mg 3 Sb 2 has high Seebeck coefficient and low lattice thermal conductivity which is 0.7 ~0.9 Wm À 1 K À 1 at RT. [24] Unfortunately, this compound has a low electrical conductivity, [25] which originates from its low carrier concentration and carrier mobility.…”

“…On the other hand, the environmental compatibility, raw material cost and service performance of thermoelectric materials have aroused great attention in recent years [7–8] . Ideal thermoelectric materials not only should possess high thermoelectric performance, but also meet the requirements of non‐toxic, good chemical stability, and thermal stability in practical applications [9–15] . Nowadays, many tellurides have been developed as state‐of‐the‐art thermoelectric materials, such as Bi 2 Te 3 , PbTe, SnTe and GeTe‐AgSbTe 2 [16–21] .…”