[17p-C301-1~11] 9.4 Thermoelectric conversion

4:30 PM - 4:45 PM JST(7:30 AM - 7:45 AM UTC)Presentation by Applicant for JSAP Young Scientists Presentation AwardEnglish Presentation

[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)

Keywords:

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.