MoSi2-type narrow band gap intermetallic compound Al6Re5Si4 as a thermoelectric material. Issue 40 (7th July 2015)

• Record Type: Journal Article
• Authors: Takagiwa, Y.; Utada, S.; Kanazawa, I.; Kimura, K.
• Is Part Of: Journal of materials chemistry. Volume 3:Issue 40(2015)
• Page Start: 10422
• Page End: 10429
• Publication Date: 2015-07-07
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c5tc01608h
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : The thermoelectric properties of MoSi2 -type intermetallic compound Al6 Re5 Si4 (investigated compositions: Al6− x Re4.7 Si4+ x ( x = 0–0.9)) related to TiSi2 -type narrow band gap intermetallic compounds were systematically investigated. Abstract : The thermoelectric properties of MoSi2 -type intermetallic compound Al6 Re5 Si4 (investigated compositions: Al6− x Re4.7 Si4+ x ( x = 0–0.9)) related to TiSi2 -type narrow band gap intermetallic compounds were systematically investigated. A first-principles band structure calculation implies that this compound forms a narrow band gap in the electronic density of states that will be suitable for obtaining a large power factor. Indeed, the maximum power factor is 1.65 mW m −1 K −2 for the sample with x = 0.8. The Al6− x Re4.7 Si4+ x ( x = 0–0.8) samples show degenerate semiconductor behavior as p-type materials; the temperature coefficient of the electrical conductivity is negative and the positive Seebeck coefficient increases with increasing temperature. A negative Seebeck coefficient is observed in the Si-rich sample with x = 0.9, which is understood by shifting the Fermi level to the conduction band. The estimated band gap is 0.53 eV from the Arrhenius plot. Because of a simple crystal structure, a relatively high thermal conductivity ranging from 7.6 to 13.5 W m −1 K −1 is observed at 300 K. The maximum dimensionless figure-of-merit of 0.19 at 973 K is close to the optimal value predicted by a single parabolic band model.