Fe segregation as a tool to enhance electrical conductivity of grain boundaries in Ti(Co, Fe)Sb half Heusler thermoelectrics. (1st May 2023)

• Record Type: Journal Article
• Authors: Bueno Villoro, Ruben; Wood, Maxwell; Luo, Ting; Bishara, Hanna; Abdellaoui, Lamya; Zavanelli, Duncan; Gault, Baptiste; Snyder, Gerald Jeffrey; Scheu, Christina; Zhang, Siyuan
• Is Part Of: Acta materialia. Volume 249(2023)
• Publication Date: 2023-05-01
• Subjects: Grain boundaries -- Half Heusler intermetallics -- Thermoelectrics -- Characterization -- Electrical conductivity; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2023.118816
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: Complex microstructures are found in many thermoelectric materials and can be used to optimize their transport properties. Grain boundaries in particular scatter phonons, but they often impede charge carrier transfer at the same time. Designing grain boundaries in order to offer a conductive path for electrons is a substantial opportunity to optimize thermoelectrics. Here, we demonstrate in TiCoSb half Heusler compounds that Fe-dopants segregate to grain boundaries and simultaneously increase the electrical conductivity and reduce the thermal conductivity. To explain these phenomena, three samples with different grain sizes are synthesized and a model is developed to relate the electrical conductivity with the area fraction of grain boundaries. The electrical conductivity of grain interior and grain boundaries is calculated and the atomic structure of grain boundaries is studied in detail. Segregation engineering in fine-grained thermoelectrics is proposed as a new design tool to optimize transport properties while achieving a lower thermal conductivity. Graphical abstract: