Novel Ge-Sb-Te thermoelectric materials: A demonstration for an efficient diffusion couple technique in expediently exploiting new thermoelectric materials

An efficient diffusion couple technique is proposed for rapid screening of potential thermoelectric materials and it has been explored in a (GeTe)_m (Sb₂Te₃)_n pseudobinary system. In this study, a combinatorial sample library of GeTe-Sb₂Te₃ diffusion couple with rich compositions and structures was prepared by plasma activation sintering (PAS). The relationship among composition, structure and performance of the materials was revealed by analyzing the chemical composition, crystal structure and thermoelectric properties of the microdomains in the combinatorial sample library, so as to achieve the purpose for rapid identification of Ge-Sb-Te compounds with excellent thermoelectric properties. The scanning results of the Seebeck coefficient of the samples library show that the sample with potential high thermoelectric performance has a chemical composition near Ge_33.1Sb_13.7Te_53.2. The bulk materials with compositions in the vicinity of Ge_33.1Sb_13.7Te_53.2 were prepared by a conventional melting and PAS process. Among these bulk samples, the one with a nominal composition of Ge₃₈Sb_10.3Te_51.7 achieves a maximum ZT value of 0.55 at 673 K, indicating that the constituent phases Ge_0.77Sb_0.154Te₁ and Ge_3.37Sb_1.63Te₆ observed in this sample could be potential candidates with excellent thermoelectric properties. These two ternary compounds should be investigated for further optimization. The results of this study provide a reference for the application of combinatorial metrology for screening and optimizing new thermoelectric materials.