Thermoelectric and Mechanical Properties of Environmentally Friendly Mg₂Si_0.3Sn_0.67Bi_0.03/SiC Composites

Abstract

In this work, polycrystalline n-type Mg2Si0.30Sn0.67Bi0.03 dispersed with x wt % β-SiC nanoparticles (x = 0, 0.5, 1.0, 1.5, and 3.0) thermoelectric materials were fabricated by a solid-state reaction in a low-cost container, consolidated by hot-pressing. We obtained figure of merit values zT above 1.4 at 773 K along with enhanced mechanical properties by adding β-SiC into an Mg2Si0.30Sn0.67Bi0.03 matrix. Incorporation of SiC nanoparticles has thusly simultaneously increased toughness and, depending on the SiC content, thermoelectric performance. The peak figure of merit was improved from zT = 1.33 for Mg2Si0.30Sn0.67Bi0.03 to 1.45 for Mg2Si0.30Sn0.67Bi0.03 with 3 wt % at 773 K.

Large Scale Solid State Synthetic Technique for High Performance Thermoelectric Materials: Magnesium-Silicide-Stannide

“…Correspondingly, we determined a typical Hall carrier concentration of 2.6 × 10 20 cm –3 and mobility of 60 cm 2 V –1 s –1 , slightly higher than the values obtained from a typical gram sample of nominally the same stoichiometry prepared in our laboratory (2.4 × 10 20 cm –3 and mobility of 53 cm 2 V –1 s –1 ) …”

“…45 Correspondingly, we determined a typical Hall carrier concentration of 2.6 × 10 20 cm −3 and mobility of 60 cm 2 V −1 s −1 , slightly higher than the values obtained from a typical gram sample of nominally the same stoichiometry prepared in our laboratory (2.4 × 10 20 cm −3 and mobility of 53 cm 2 V −1 s −1 ). 38 Seebeck coefficient measurements (Figure S7) showed the expected temperature dependence: the absolute values increased with temperature as seen in Figure 2b. The extra electrons from the Bi atoms occupying the Cn sites populated the conduction bands, and therefore the Seebeck coefficient was negative as expected.…”

“…A variety of synthetic methods have been performed to obtain Mg 2 Cn based compounds and to improve the thermoelectric properties including solid state reaction, flux synthesis method, mechanical alloying, hot-pressing, spark-plasma-sintering (SPS), , melt-casting, , and nanoadditions. , The use of expensive sacrificial reaction crucibles such as BN or tantalum crucibles is standard to avoid Mg volatilization and reaction with the container. Recently we demonstrated that potentially better results may be achieved employing non-reusable small scale graphite containers while heating under argon flow …”

Current State‐of‐the‐Art in the Interface/Surface Modification of Thermoelectric Materials

“…Among the several types of second phases that have been incorporated into TE materials to enhance their zT value, silicon carbide nanoparticles have attracted significant interest. Many semiconductors, such as SiC, [ 131–142 ] MgB 2 , [ 143,144 ] TiN, [ 145,146 ] B, [ 147–149 ] and others, [ 150–152 ] have been confirmed to improve both the mechanical and thermoelectric performance of TE materials.…”

“…[ 157,158 ] Also, nanoparticle dispersion aids in the dislocation of pile‐up stresses and hinders the generation of cracks, as well as their further propagation, thereby strengthening the fracture toughness. [ 132,134,136,159 ] The presence of second phases can trigger the generation of porosities, however, impacting in the process the relative density and, by extension, material hardness. [ 154 ]…”