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

Sylvain Le Tonquesse (1, 2) , Wenhao Zhang (3, 4) , Bhuvanesh Srinivasan (1, 2) , Bruno Fontaine (5) , Takanobu Hiroto (1) , Takao Mori (3, 4, 1) , Jean-François Halet (1, 2) , David Berthebaud (1, 2) , Tohru S. Suzuki (1)

1 NIMS - National Institute for Materials Science
2 LINK - Laboratory for Innovative Key Materials and Structures
3 WPI-MANA - International Center for Materials Nanoarchitectonics
4 Université de Tsukuba = University of Tsukuba
5 ISCR - Institut des Sciences Chimiques de Rennes

Transition metal silicides constitute a promising class of inexpensive and nontoxic thermoelectric materials showing competitive properties. This article reports an efficient process to synthesize highly textured polycrystalline CrSi2 by performing slip casting under a strong magnetic field. The crystallographic texture of spark plasma sintered samples, characterized by electron backscattered and X-ray diffraction techniques, showed a fiber texture symmetry with the c-axis of hexagonal CrSi2 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, parallel to c, reaching a maximum value of 200 mu V K-1 at 650 K, inducing a power factor parallel to c twice higher than perpendicular to 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 parallel to 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.

Domaines: Chimie

Sylvain Le Tonquesse, Wenhao Zhang, Bhuvanesh Srinivasan, Bruno Fontaine, Takanobu Hiroto, et al.. Improvement of Thermoelectric Properties via Texturation Using a Magnetic Slip Casting Process-The Illustrative Case of CrSi2. Chemistry of Materials, 2022, 34 (3), pp.1143-1156. ⟨10.1021/acs.chemmater.1c03608⟩. ⟨hal-03553181⟩