Boosting thermoelectric performance is challenging due to the intricate interplay between electrical and thermal transport properties.This study focuses on Zr vacancy-filled p-type Ti_(2)Zr_(2−x)Hf_(2)Nb_(2)Fe_(5.6)Ni...Boosting thermoelectric performance is challenging due to the intricate interplay between electrical and thermal transport properties.This study focuses on Zr vacancy-filled p-type Ti_(2)Zr_(2−x)Hf_(2)Nb_(2)Fe_(5.6)Ni_(2.4)Sb_(8)-based thermoelectric materials to explore how Zr vacancies affect their structural and transport characteristics.Density functional theory calculations demonstrate that Zr vacancies induce proximal contraction/distal relaxation,strengthening lattice distortion while preserving the intrinsically intense phonon scattering in Ti_(2)Zr_(2−x)Hf_(2)Nb_(2)Fe_(5.6)Ni_(2.4)Sb_(8) samples.The intensified asymmetric electron localization between adjacent anions and the cation vacancies softens local chemical bonds.Microscopic investigations reveal that Ti_(2)Zr_(2−x)Hf_(2)Nb_(2)Fe_(5.6)Ni_(2.4)Sb_(8) alloys with an optimal number of Zr vacancies balance the competing effects of carrier and phonon transport mechanisms by regulating multi-scale defects.Introducing appropriate Zr vacancies optimizes both the Seebeck coefficient andκL without greatly affecting electrical conductivity and weight mobility,achieving a 23%maximum power factor improvement and roughly 10%κL reduction.The bipolar diffusion effect is effectively suppressed to negligible levels by energy filtering effects,thus ensuring high-temperature stability.The maximum ZT of Ti_(2)Zr_(2−x)Hf_(2)Nb_(2)Fe_(5.6)Ni_(2.4)Sb_(8) and Ti_(2)Zr_(2−x)Hf_(2)Nb_(2)Fe_(5.6)Ni_(2.4)Sb_(8) is 30%higher than that of pristine samples without Zr vacancies.These findings are the first demonstration of vacancy engineering as a promising strategy in p-type double half-Heusler alloys to enhance their thermoelectric performance and decouple intertwined transport parameters.展开更多
基金supported by the National Key Research and Development Program of China(no.2018YFB0703400)the National Natural Science Foundation of China(no.51271034)+1 种基金Taishan Scholar Program of Shandong Province(no.tsqn202306225)Jinan City-School Integration Development Strategy Project(no.JNSX2023018).
文摘Boosting thermoelectric performance is challenging due to the intricate interplay between electrical and thermal transport properties.This study focuses on Zr vacancy-filled p-type Ti_(2)Zr_(2−x)Hf_(2)Nb_(2)Fe_(5.6)Ni_(2.4)Sb_(8)-based thermoelectric materials to explore how Zr vacancies affect their structural and transport characteristics.Density functional theory calculations demonstrate that Zr vacancies induce proximal contraction/distal relaxation,strengthening lattice distortion while preserving the intrinsically intense phonon scattering in Ti_(2)Zr_(2−x)Hf_(2)Nb_(2)Fe_(5.6)Ni_(2.4)Sb_(8) samples.The intensified asymmetric electron localization between adjacent anions and the cation vacancies softens local chemical bonds.Microscopic investigations reveal that Ti_(2)Zr_(2−x)Hf_(2)Nb_(2)Fe_(5.6)Ni_(2.4)Sb_(8) alloys with an optimal number of Zr vacancies balance the competing effects of carrier and phonon transport mechanisms by regulating multi-scale defects.Introducing appropriate Zr vacancies optimizes both the Seebeck coefficient andκL without greatly affecting electrical conductivity and weight mobility,achieving a 23%maximum power factor improvement and roughly 10%κL reduction.The bipolar diffusion effect is effectively suppressed to negligible levels by energy filtering effects,thus ensuring high-temperature stability.The maximum ZT of Ti_(2)Zr_(2−x)Hf_(2)Nb_(2)Fe_(5.6)Ni_(2.4)Sb_(8) and Ti_(2)Zr_(2−x)Hf_(2)Nb_(2)Fe_(5.6)Ni_(2.4)Sb_(8) is 30%higher than that of pristine samples without Zr vacancies.These findings are the first demonstration of vacancy engineering as a promising strategy in p-type double half-Heusler alloys to enhance their thermoelectric performance and decouple intertwined transport parameters.
