<p>This study investigated the metallurgical aspects of interface formation and evolution between pure CoSb₃ skutterudite thermoelectric material and various diffusion barrier systems. Four barrier compositions (Co–W, Co–Ni–W, Co–Cr, and Co–Ni–Cr) were selected for evaluation, the barriers being fabricated and consolidated using a powder metallurgy technique. The joint formation, interface reactivity, and the evolution of the reaction layers were analyzed using scanning electron microscopy and energy-dispersive spectroscopy. The results showed that controlling the consolidation temperature reduced porosity in the barriers, but higher temperatures increased interfacial reactivity, especially in Co–Ni–Cr systems. Post-annealing studies revealed significant diffusion layer growth, with Co–Ni–W showing the highest diffusion rates. Seebeck potential mapping confirmed the electrical stability of the joints, with minimal degradation in thermoelectric properties noted after heat treatment. These findings provide insights into optimizing diffusion barriers for enhanced performance and reliability of thermoelectric modules.</p>