[17p-C301-1~11] 9.4 熱電変換

16:30 〜 16:45奨励賞エントリー英語発表

[17p-C301-11] Toxic-Element-Free Inverse-Perovskite Oxide Ba₃BO (B = Si, Ge) with Low Thermal Conductivity and High Thermoelectric Performance

〇(PC)XINYI HE¹, Shigeru Kimura¹, Takayoshi Katase¹, Terumasa Tadano², Satoru Matsuishi¹, Hidenori Hiramatsu¹, Hideo Hosono¹, Toshio Kamiya¹ (1.MDX ES, Tokyo Tech, 2.NIMS)

キーワード：

Thermoelectric oxides、Lattice thermal conductivity

To date, high energy conversion efficiency (ZT) materials are primarily demonstrated in heavy metal chalcogenides, but the use of toxic elements (eg: Pb and Te) is not preferred for widespread practical applications. This study proposes inverse perovskite-type oxide Ba₃BO (B = Si, Ge) as a novel class of toxic-element-free thermoelectric materials with high ZT reported so far. We demonstrate that undoped Ba₃BO bulks experimentally exhibit rather high ZT = 0.16–0.84 at T = 300–623 K, and theoretically estimated to 2.14 at T = 600 K when optimally doped, based on the first-principles carrier and phonon transport calculations. We elucidate the origin of high ZT for Ba₃BO. Ba₃BO bulks exhibit remarkably low lattice thermal conductivity stemming from the highly distorted O–Ba₆ octahedra framework with weak O–Ba ionic bonds, which provides low phonon group velocity and strong phonon scattering. Additionally, Ba₃BO achieves a high PF due to the favorable band structures, where valence bands around Fermi level arises from the p state of the negatively charged Banion with large ion size, and their highly dispersive bands with multiple valley degeneracy enable both high σ and high S.