Abstract Here, the effects of variable-valence element Sm doping on the thermoelectric performance of BiCuSeO are studied. The Bi1-xSmxCuSeO (x = 0, 0.025, 0.05, and 0.10) oxyselenides were prepared by a two-step solid state reaction and spark plasma sintering. Experimental measurements and first-principles calculations indicated that Sm2+ and Sm3+ coexisted in the samples. The electrical conductivity of the Sm-doped samples was greater than that of pristine BiCuSeO mainly because the holes introduced by Sm2+ doping increased the carrier concentration, and the shift of the Fermi level by Sm3+ substitution changed the band gap. The combination of a moderate Seebeck coefficient and relativity low thermal conductivity, gave a maximum ZT value of 0.65 at 823 K for Bi0.975Sm0.025CuSeO, which is approximately 25 % higher than that of the pristine sample. This study indicates that doping with rare-earth variable-valence elements is an efficient approach to designing high-performance thermoelectric materials.

中文翻译：

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变价元素 Sm 掺杂的 BiCuSeO 氧硒化物的热电性能增强

摘要 在此，研究了可变价元素 Sm 掺杂对 BiCuSeO 热电性能的影响。Bi1-xSmxCuSeO (x = 0、0.025、0.05 和 0.10) 硒化物是通过两步固态反应和放电等离子体烧结制备的。实验测量和第一性原理计算表明 Sm2+ 和 Sm3+ 共存于样品中。Sm 掺杂样品的电导率大于原始 BiCuSeO 的电导率，主要是因为 Sm2+ 掺杂引入的空穴增加了载流子浓度，Sm3+ 取代导致的费米能级移动改变了带隙。中等塞贝克系数和相对低热导率相结合，Bi0.975Sm0.025CuSeO 在 823 K 时的最大 ZT 值为 0.65，比原始样品的 ZT 值高约 25%。