Unified contact layer and low-temperature transient liquid phase interconnection for high-performance all-Mg-based thermoelectric devices
Shanghao Chen, Tianyu Zhang, Jinxuan Cheng, Baopeng Ma, Xiaojing Ma, Xiaofang Li, Li Yin, Linmao Wen, Jun Mao, Feng Cao, Qian Zhang
Abstract
Thermoelectric technology enables direct conversion of untapped low-grade waste heat into electrical energy. Mg₃(Sb, Bi)₂ and MgAgSb, with their excellent thermoelectric performance near room temperature, have emerged as cost-effective and environmentally friendly alternatives to Bi₂Te₃-based materials. However, the development of high-performance Mg-based thermoelectric devices faces significant challenges due to the inherent high chemical reactivity and volatility of Mg elements, coupled with the phase transition-induced degradation of thermoelectric properties in MgAgSb, which collectively led to poor interfacial contacts and device integration. In this study, a Mg-based thermoelectric device consisting of n-type Mg₃(Sb, Bi)₂ and p-type MgAgSb has been fabricated with Mg₂Ni as the unified contact layer for both materials. The Ni-Sn transient liquid-phase (TLP) low-temperature bonding technology has been employed for the integration of the thermoelectric device. In addition, thermal aging and cycling tests confirmed the long-term stability of the Mg₂Ni/TE contact interfaces and the Ni-Sn intermetallic compound (IMC) joints. Notably, the device with segmented n-type legs achieves an exceptional conversion efficiency of ∼10.8% at a temperature difference of 300 K. This work promotes the application of high-performance, environmentally friendly Mg-based thermoelectric devices in low-grade waste heat recovery.