Bismuth oxyselenide (Bi2O2Se) attracts great interest as a potential n-type complement to p-type thermoelectric oxides in practical applications. Previous investigations were generally focused on polycrystals. Here, we performed a study on the thermoelectric properties of Bi2O2Se single crystals. Our samples exhibit electron mobility as high as 250 cm2.V−1.s−1 and thermal conductivity as low as 2 W.m−1.K−1 near room temperature. The maximized figure of merit is yielded to be 0.188 at 390 K, higher than that of polycrystals. Consequently, a rough estimation of the phonon mean free path (ℓph) from the kinetic model amounts to 12 A˚ at 390 K and follows a T−1 behavior. An extrapolation of ℓph to higher temperatures indicates that this system approaches the Ioffe-Regel limit at about 1100 K. In light of the phonon dispersions, we argue that the ultralow ℓph is attributed to intense anharmonic phonon-phonon scattering, including Umklapp process and acoustic to optical phonon scattering. Our results suggest that single crystals provide a further improvement of thermoelectric performance of Bi2O2Se.
@article{arxiv.2108.13809,
title = {Thermoelectric properties of Bi2O2Se single crystals},
author = {Jialu Wang and Wanghua Hu and Zhefeng Lou and Zhuokai Xu and Xiaohui Yang and Tao Wang and Xiao Lin},
journal= {arXiv preprint arXiv:2108.13809},
year = {2021}
}