Synthesis and characterization of bulk Si-Ti nanocomposite and comparisons of approaches for enhanced thermoelectric properties in nanocomposites composed of Si and various metal silicides

摘要

Si-based materials are considered as promising candidates for thermoelectric materials, owing to several advantages such as non-toxicity, abundance, and high stability. One of the strategies to develop high-efficiency Si-based thermoelectric materials with enhanced figure of merit zT is increasing the μ_H/κ_(lat) ratio, where μ_H and κ_(lat) are the Hall mobility and lattice thermal conductivity, respectively. In the present study, we synthesize a bulk Si-Ti nanocomposite composed of Si and Ti silicide by a combined method of melt-spinning and spark plasma sintering and examine the thermoelectric properties. The obtained results are compared with the data for Si-V and Si-Ni nanocomposites reported previously by the authors' group. In the comparison, we focus on (1) size and distribution of the precipitates, (2) the interface between Si and the precipitates, and (3) volume fraction of the precipitates; and investigate the effects of these three factors on keeping high μ_H and reduction of κ_(lat·) Based on the comparison, it is revealed that the uniform distribution of the precipitates and the coherent interface between Si and metal silicide lead to large μ_H/κ_(lat) ratio and thus enhanced zT in the nanocomposites composed of Si and metal silicides.