Al-Si Alloy as a Diffusion Barrier for GeTe-Based Thermoelectric Legs with High Interfacial Reliability and Mechanical Strength.

Abstract

To build high-performance thermoelectric (TE) devices for power generation, a suitable diffusion-barrier layer between the electrodes and the TE materials in a TE device is generally required for achieving good interfacial connection with high reliability, high mechanical strength but low electrical and thermal contact resistivities. GeTe-based materials have attracted great attention recently due to their high TE performance in the mid-temperature range, but studies on their TE devices are still limited. Here, we selected the Al66Si34 alloy as a diffusion barrier for GeTe-based TE legs based on the matching test of the coefficient of thermal expansion. The good connection between Al66Si34 and Ge0.9Sb0.1TeB0.01 is realized by the interfacial reaction, where the randomly distributed Al2Te3 and Ge precipitates are formed at the interface of the joint. The as-prepared interfacial electrical contact resistivity can be as low as 20.7 μΩ·cm2 and only slightly increases to 26.1 μΩ·cm2 after 16 days of aging at 500 °C. Moreover, the shear strength of the joints can be as high as 26.6 MPa and unexpectedly increases to 41.7 MPa after 16 days of aging. The thickness of the reaction layer tends to be stabilized after 8 days of aging and nearly does not change after further aging to 16 days, which may be ascribed to the drag effect from Si and the secondary Ge phases. These results demonstrate the great potential of the Al-Si alloy as a diffusion barrier for GeTe-based TE devices with high performance.