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A1: Low temperature materials

Uniformity study of large sized ingots of Bi2Te3-based thermoelectric materials prepared with the Spark Plasma Sintering (SPS) method

Chaehoon Kim1, Atta Ullah Khan2, Yongsang Cho1, Hyungeui Lee1*, Hyuksoo Lee1, Takao Mori2
1 LG Innotek Components R&D Center 55, Hanyangdaehak-ro, Sangnok-gu, Ansan-si, 426-791, Korea2 National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba 305-0044, Japan

Development of thermoelectric materials is being vigorously carried out throughout the world now, utilizing state-of-the-art processing methods [1]. In this study, large sized ingots of both n- and p-type Bi2Te3-based thermoelectric materials were fabricated by the Spark Plasma Sintering (SPS) method, and the variation of ZT values existing within the pellet was analyzed in careful detail.

In the fabrication of lab-scale pellets (~10mm), thermoelectric properties (electric and thermal conductivity, Seebeck coefficient) are easily controlled by SPS process conditions and no significant differences on thermoelectric properties are found within the pellet. However, in the case of the scale-up of thermoelectric materials based on Bi2Te3, we have found that the uniformity of properties within the pellet is strongly influenced by such conditions. Our research focused on improving the uniformity of the thermoelectric properties within the pellet by optimizing SPS process conditions (i.e. heating program with variations of heating rate, temperature, duration, and applied pressure) for the scaled-up ingots (10~100mm) and performing detailed analysis of thermoelectric properties, morphology, etc. over a fine matrix.

We have achieved more than 98% of uniformity from the center to edge of 50mm Bi2Te3-based ingots under specific SPS process conditions which is very promising for scaled-up applications.

[1] Thermoelectric Nanomaterials, ed. K. Koumoto and T. Mori, (Springer, Heidelberg, 2013).