Enhancing Interfacial Stability of GeTe-Based Thermoelectric Junction Using an Amorphous Al–Ni–Ti Diffusion Barrier

GeTe-based thermoelectric (TE) materials are promising for midtemperature applications, but their high reactivity with common metal electrodes necessitates effective diffusion barriers. This study investigates amorphous Al–Ni–Ti alloys, specifically Al₆₀Ni₁₀Ti₃₀, as diffusion barriers between GeTe-based TE materials (Ge_0.89Sb_0.1In_0.01Te) and Cu electrodes. Through element screening based on thermodynamic compatibility and coefficient of thermal expansion (CTE) matching, Al and Ti were identified for their suitable reactivity with GeTe, with Ni added to enhance interfacial bonding. Interfacial characterization of GeTe/barrier/Cu joints revealed well-bonded interfaces. High-temperature aging tests at 773 K for 216 h demonstrated the superior stability of the amorphous barrier, exhibiting a reaction layer thickness approximately 60% less than its crystalline counterpart and maintaining lower interfacial contact resistivity. Joints fabricated using a one-step hot pressing method for the GeTe/barrier/Cu composite, followed by sintering to Cu electrodes with nano silver paste, achieved a shear strength of 13 MPa, comparable to the bulk GeTe material, with fractures occurring within the GeTe matrix and at the intermetallic compound/GeTe interface. These findings highlight amorphous Al₆₀Ni₁₀Ti₃₀ as a reliable and more stable diffusion barrier, offering a promising solution for enhancing the long-term operational stability of midtemperature GeTe-based TE modules.