Reduced Thermal Conductivity of Mg₂(Si, Sn) Solid Solutions by a Gradient Composition Layered Microstructure

Abstract

Solid solutioning of Mg 2 (Si, Sn) has been a promising approach in reducing thermal conductivity and leads to improvement of thermoelectric performance. In addition to the Mg 2 (Si, Sn) solid solutions, we have noticed a layered structure with a gradient composition, which is formed by nonequilibrium solidification and peritectic reaction process and can provide further reduction of thermal conductivity of the Mg 2 (Si, Sn) solid solutions. All layers of the layered structure have the same face-centered cubic-based structure but varying Sn/Si concentration ratios in each layer. The interfaces between the layers are semi-coherent, reticulating with different numbers of misfit dislocations. Such an interfacial structure brings large numbers of phonon-scattering sources, resulting in further reduction of thermal conductivity in the Mg 2 (Si, Sn) solid solutions. Consequently, the undoped Mg 2 Si 0.75 Sn 0.25 containing a higher density of the layered structure has relatively lower thermal conductivity, 1.9 W m −1 K −1 at 523 K, than Mg 2 Si 0.25 Sn 0.75 with a much lower density of the layered structure, 2.3 W m −1 K −1 at 523 K.

Synergistic modulation of the thermoelectric performance of melt-spun p-type Mg2Sn via Na2S and Si alloying

“…However, because of the scarcity of Te and the toxicity of Pb, it is also crucial to explore high-performance materials consisting of earthabundant and non-toxic elements for widespread applications. [14][15][16][17][18][19][20] Mg 2 (Si,Sn)-based materials are regarded as cost-effective and environmentally friendly thermoelectrics, which are promising for medium-temperature applications. Intensive attention has been focussed on n-type Mg 2 (Si,Sn), which has already achieved high zT values over 1.…”

(Ti0.2V0.2Cr0.2Nb0.2Ta0.2)2AlC–(Ti0.2V0.2Cr0.2Nb0.2Ta0.2)C high‐entropy ceramics with low thermal conductivity

“…Notably, κ l is a relatively independent parameter, and thus decreasing κ l should be an effective way to enhance TE properties. [7][8][9] The layered compounds with the general chemical formula M n+1 AX n are collectively referred to the MAX phases, where M is an early transition metal, A is an Agroup element (mostly IIIA and IVA groups), and X is carbon and/or nitrogen elements, and n is in the range 1−3. 10 These phases are composed of near-close-packed layers of covalent M 6 X octahedrons and intercalated with metal-like A atom layers.…”

Enhancing Thermoelectric Properties of (Cu2Te)1−x-(BiCuTeO)x Composites by Optimizing Carrier Concentration

“…To get the ideal thermoelectric performance, the PF of materials can be raised by band engineering, quantum confinement effects and electron energy barrier filtering [ 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. Besides, can be reduced by nanostructures all-scale hierarchical architecture engineering, which is able to increase the scattering of short, medium and long wavelength phonons, and entropy engineering [ 17 , 18 , 19 , 20 , 21 , 22 ].…”