Influence of PCA on thermoelectric properties and hardness of nanostructured Ba–Cu–Si clathrates. (15th December 2015)

• Record Type: Journal Article
• Authors: Zolriasatein, A.; Yan, X.; Bauer, E.; Rogl, P.; Shokuhfar, A.; Paschen, S.
• Is Part Of: Materials & design. Volume 87(2015:Dec.)
• Page Start: 883
• Page End: 890
• Publication Date: 2015-12-15
• Subjects: Nanostructured materials -- Clathrates -- Mechanical milling -- Thermoelectric properties -- Hardness -- Microstructure; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2015.08.096
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: Nanostructuring has been considered an effective approach to enhance the thermoelectric (TE) performance of materials by reducing their lattice thermal conductivity. In the present study, we show the influence of a process control agent (PCA) for ball milling, Stearic acid (SA), on the nano- and microstructure and thermoelectric properties of type-I clathrates in the Ba–Cu–Si system, which are promising candidates for TE applications. The SA effectively reduces cold welding and prevents particle agglomeration during ball milling. Consequently, it increases the powder yield and the milling efficiency. Smaller grain/crystallite sizes are obtained in the as-milled powders than without SA. Importantly, the SA forms nano-layers around the clathrate particles, which inhibit the grain growth during the hot pressing process used for powder compaction. Therefore, smaller grain sizes are also obtained in the hot-pressed samples. They show increased hardness and reduced thermal conductivity but also increased electrical resistivity. However, as the phonon transport is more strongly degraded than the charge transport, we observe 15% enhancement in the dimensionless thermoelectric figure of merit ZT by adding the PCA. Graphical abstract: Highlights: Process control agent improves thermoelectric efficiency of nanostructured clathrates. Stearic acid (SA) increases powder yield and efficiency of ball milling process. SA nanolayers surround nanoparticles and suppress grain growth during hot pressing. SA reduces thermal conductivity and increases hardness of clathrate.