Improvement of Thermoelectric Properties via Texturation Using a Magnetic Slip Casting Process–The Illustrative Case of CrSi₂

Abstract

Transition metal silicides constitute a promising class of inexpensive and non-toxic thermoelectric materials showing competitive properties. This article reports an ef-1 Accepted manuscript / Final version ficient process to synthesize highly textured poly-crystalline CrSi 2 by performing slip casting under a strong magnetic field. The crystallographic texture of spark plasma sintered samples, characterized by electron back-scattered and X-ray diffraction techniques showed a fiber texture symmetry with the c-axis of hexagonal CrSi 2 aligning preferentially along the magnetic field direction. The thermoelectric properties measured both parallel and perpendicular to the c-axis texture direction showed a large anisotropy. In particular, a significantly higher Seebeck coefficient was measured c reaching a maximum value of 200 µV K −1 at 650 K, inducing a power factor c twice higher than ⊥c with an average value of 2.2 mW m −1 K −2 . Density functional theory and transport property calculations revealed that an anisotropic two-band model can explain the higher thermoelectric property along the c-axis direction, which can be traced to Cr-Cr bonding interactions along this direction. The estimated thermoelectric figure of merit ZT c was improved to 0.20 at 773 K. This is 50 % higher than that measured for randomly oriented samples and comparable to that observed for single crystals. Such a performance boost can certainly be reiterated for other types of thermoelectric materials using the efficient magnetic slip-casting process reported in this article.

Enhanced High-Temperature Thermoelectric Performance of Yb4Sb3 via Ce/Bi Co-doping and Metallic Contact Deposition for Device Integration

“…Thus, the choice of TE materials to make a generator primarily depends on the operational temperature of the target application. Previous research studies have primarily focused on materials suitable for near-room-temperature applications (300−400 K), such as Bi 2 Te 3 2 or Mg 3 Bi 2 , 3 or for midtemperature applications (600−800 K), such as PbTe, 4,5 skutterudite CoSb 3 , 6,7 transition-metal silicides, 8,9 or SnSe. 10,11 T h i s c o n t e n t i s Nonetheless, fewer studies have been devoted to hightemperature applications (1000−1200 K) despite their significant potential in heavy industry and space exploration.…”

“…Thus, the choice of TE materials to make a generator primarily depends on the operational temperature of the target application. Previous research studies have primarily focused on materials suitable for near-room-temperature applications (300–400 K), such as Bi 2 Te 3 or Mg 3 Bi 2 , or for mid-temperature applications (600–800 K), such as PbTe, , skutterudite CoSb 3 , , transition-metal silicides, , or SnSe. , Nonetheless, fewer studies have been devoted to high-temperature applications (1000–1200 K) despite their significant potential in heavy industry and space exploration. Si–Ge alloys have historically been the most investigated materials for high-temperature applications, but new materials exhibiting promising properties have emerged, such as the Zintl phase Yb 14 MSb 11 (M = Mg, Mn), , Heusler alloys, or borides. , However, to improve the industrial potential of TE generators in this temperature range, new materials demonstrating superior performance and stability need to be discovered.…”

Fabrication of c‐axis–oriented AlN bulk ceramics using a rotating magnetic field

“…Crystallographic orientation, even in diamagnetic ceramics, has been successfully achieved by utilizing a strong magnetic field. This processing can be applied to a wide variety of feeble magnetic ceramics such as Al 2 O 3 , lanthanum silicate oxyapatite, CrSi 2 , and Al 2 (WO 4 ) 3 14–20 . An asymmetric crystal structure should exhibit anisotropic magnetic susceptibility.…”

“…This processing can be applied to a wide variety of feeble magnetic ceramics such as Al 2 O 3 , lanthanum silicate oxyapatite, CrSi 2 , and Al 2 (WO 4 ) 3 . [14][15][16][17][18][19][20] An asymmetric crystal structure should exhibit anisotropic magnetic susceptibility. When particles with anisotropic magnetic susceptibility are placed in a magnetic field, a magnetic torque is generated from the interaction between this anisotropy and the applied magnetic field.…”