Influence of PCA on thermoelectric properties and hardness of nanostructured Ba–Cu–Si clathrates

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 asmilled 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 * Corresponding authors. ACCEPTED MANUSCRIPT2 transport, we observe 15 % enhancement in the dimensionless thermoelectric figure of merit ZT by adding the PCA.

A comprehensive review of thermoelectric technology: Materials, applications, modelling and performance improvement

“…The assembly of TEG devices is still particularly challenging, and consequently these devices have been applied only in niche applications [17]. With regard to TE materials, there is a problem of wide lattice thermal conductivity whereby nanostructuring has been considered as an effective approach to enhance the TE performance of materials by reducing their lattice thermal conductivity [18]. The introduction of large concentrations of lattice vacancies in silicon nano-films is noted for creating more than a 20-fold reduction in thermal conductivity, while Seebeck coefficient and electrical conductivity are largely maintained [19].…”

The status of refrigeration techniques for vaccine storage and transportation in low-income settings

“…Most of the current research regarding thermoelectric refrigeration focuses on improving the ZT value of the materials while reducing their costs. Zolriasatein et al [94] showed that the grinding process of a material could influence its thermoelectric properties: as they added stearic acid during the grinding, the figure of merit of the material was enhanced by 15%. Hinterleitner et al [95] developed a new material, made from a thin layer of iron, vanadium, tungsten and aluminium applied to a silicon crystal, which ensures a ZT value between 5 and 6 at 300°C.…”

Nanostructured clathrates and clathrate‐based nanocomposites

“…We used stearic acid, CH(CH)COH, as a process control agent (PCA). The aim is to study how the PCA influences the behavior of grain size reduction during ball milling and growth during hot pressing . The process parameters for ball milling and hot pressing were fixed according to Sections and .…”