論文雑誌「Journal of Materials Chemistry A」のカバーピクチャーを制作しました［宮崎大学］

Environmentally friendly thermoelectric sulphide Cu₂ZnSnS₄ single crystals achieving a 1.6 dimensionless figure of merit ZT
Akira Nagaoka*, Kenji Yoshino, Taizo Masuda, Taylor D. Sparks, Michael A. Scarpulla and
Kensuke Nishioka

Thermoelectrics (TEs) are an important class of technology that harvest electric power directly from heat sources. When designing both high performance and environmentally friendly TE materials, the pseudo-cubic structure has great theoretical potential to maximize the dimensionless figure of merit ZT. The TE multinary single crystal with a pseudo-cubic structure paves a new path toward manipulating valley degeneracy and anisotropy with low thermal conductivity caused by short-range lattice distortion. Here, we report a record high ZT = 1.6 around 800 K realized in a totally environmentally benign p-type Na-doped Cu₂ZnSnS₄ (CZTS) single crystal. The exceptional performance comes from a high power factor while maintaining intrinsically low thermal conductivity. The combination of the pseudo-cubic structure and intrinsic properties of the CZTS single crystal takes advantage of simple material tuning without complex techniques.

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