Title: Ni nanoparticle-based TLP sintering pastes for high-temperature joining of dissimilar electrodes in thermoelectric devices

Authors: Hyukjun Youn; Kyeongho Lee; Hyeonbin Jo; Soonil Lee; Kyu-Mann Lee; Soon-Mok Choi

Addresses: School of Energy, Materials and Chemical Engineering, Korea University of Technology and Education (KOREATECH), Cheonan, 31253, South Korea ' School of Energy, Materials and Chemical Engineering, Korea University of Technology and Education (KOREATECH), Cheonan, 31253, South Korea ' School of Energy, Materials and Chemical Engineering, Korea University of Technology and Education (KOREATECH), Cheonan, 31253, South Korea ' Department of Materials Convergence and System Engineering, Changwon National University, Changwon, 51140, South Korea ' School of Energy, Materials and Chemical Engineering, Korea University of Technology and Education (KOREATECH), Cheonan, 31253, South Korea ' School of Energy, Materials and Chemical Engineering, Korea University of Technology and Education (KOREATECH), Cheonan, 31253, South Korea

Abstract: A transient liquid phase sintering (TLPS) brazing method for high-temperature thermoelectric devices was investigated through the development of Ni-Sn-based pastes. A pressureless brazing process was also developed to address the challenge of uniform pressure application in complex structures of thermoelectric devices. A brazing evaluation method using a simplified thermoelectric module structure was established to assess paste performance. The tensile strength of joints brazed with the 43Ni-57Sn paste, corresponding to the stoichiometric composition of Ni3Sn4, was lower than expected. To improve tensile strength, a new TLPS paste with excess Sn (30Ni-70Sn) was formulated based on a mechanistic study. As a result, the tensile strengths of the Ni-Ni and Cu-Ni joints were significantly improved to 29.08 kgf/cm² and 14.49 kgf/cm², representing 1.81-fold and 3.5-fold increases, respectively. These results demonstrate that applying a Sn-excess composition in TLPS paste effectively enhances the tensile strength of pressureless TLPS brazing by promoting the formation of robust adhesive intermetallic compound (IMC) layers.

Keywords: pressureless TLPS; Ni-Sn IMC; thermoelectric module; Sn excess composition; mechanical strength.

DOI: 10.1504/IJNT.2025.152230

International Journal of Nanotechnology, 2025 Vol.22 No.1, pp.42 - 49

Published online: 11 Mar 2026 *

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