Thermoelectric performance of textured Bi2Te3-based sintered materials prepared by spark plasma sintering
- PDF / 308,691 Bytes
- 9 Pages / 612 x 792 pts (letter) Page_size
- 31 Downloads / 201 Views
S9.3.1
Thermoelectric performance of textured Bi2Te3-based sintered materials prepared by spark plasma sintering Lidong Chen, Jun Jiang, Xun Shi State Key Laboratory of High Performance Ceramics and Superfine Microstructure Shanghai Institute of Ceramics, Shanghai 200050, China ABSTRACT Thermoelectric performance of polycrystalline materials is greatly influenced by their microstructures including grain sizes, grain boundaries, grain orientations in anisotropic compounds, etc. The material microstructures are sensitive to the preparation processes and the starting materials. In the present study, n-type and p-type Bi2Te3-based sintered materials with highly preferred grain orientations have been fabricated through a spark plasma sintering (SPS) technique, by controlling the particle sizes of the starting powder and other sintering process parameters. The obtained textured Bi2Te3-based materials show a high mechanical strength as 80MPa in bending strength, which is 7 to 8 times as that of the melted ingot materials, and a significant anisotropy in thermoelectric transport properties. The optimal figure of merit (ZT) of the sintered materials in the direction perpendicular to the pressing direction (with c-axis preferred orientation) is comparable to that of the zone-melted ingots in the same crystallographic orientation.
INTRODUCTION Bi2Te3-based solid solutions, including n-type Bi2(Te,Se)3 and p-type (Bi,Sb)2Te3, have been widely used as materials for thermoelectric cooling at around room temperature for their high figure of merit [1-3]. These variety of solid solutions have a rhombohedral structure, with space group R 3 m. They are composed of atomic layers in the order of -Te (1)-Bi-Te (2)-Bi-Te (1)- along the c-axis. The Bi-Te (1) and Bi-Te (2) are mainly covalent, while the bonding between Te (1)-Te (1) layers is Van der Waal interactions. Therefore, it is easy to cleavage along the basal plane, which results in poor mechanical properties. Usually, these materials are grown by means of zone melting, Bridgman and Czochralsky techniques. These melted ingot materials exhibit excellent thermoelectric performance along the crystal-growth direction, however, have the disadvantage of poor mechanical properties. The poor mechanical properties cause difficulties in fabrication and low reliability especially for the application in the miniature thermoelectric modules [4-6]. Study on the development of Bi2Te3-based materials having both high thermoelectric performance and mechanical strength has been attracting great attention and many new fabrication method have been reported in recent years [7-13]. Spark plasma sintering (SPS) is a newly developed rapid sintering method. It is considered that discharge plasma is generated by pulsed current between particles, which causes the cleaning of powder surface and promotes the mass transport to physically contacting regions between particles [15]. SPS has been widely used to consolidate various bulk materials, such as metals, intermetallic compounds, ceramics, functionally gra
Data Loading...
