Thermoelectric properties of heavily Co-doped β-FeSi_(2)  

作　　者：Jun Cheng Lu Gan c Jiawei Zhang Jinyang Xi Lili Xi Jiong Yang Tingting Deng Pengfei Qiu Xun Shi Lidong Chen 

机构地区：[1]State Key Laboratory of High Performance Ceramics and Superfine Microstructure,Shanghai Institute of Ceramics,Chinese Academy of Sciences,Shanghai 200050,China [2]Center of Materials Science and Optoelectronics Engineering,University of Chinese Academy of Sciences,Beijing 100049,China [3]Materials Genome Institute,Shanghai University,Shanghai 200444,China [4]School of Chemistry and Materials Science,Hangzhou Institute for Advanced Study,University of Chinese Academy of Sciences,Hangzhou 310024,China

出　　处：《Journal of Materials Science & Technology》2024年第20期248-257,共10页材料科学技术（英文版）

基　　金：This work was supported by the National Natural Science Foun-dation of China(Nos.91963208,52232010,and 52122213);the Shanghai Pilot Program for Basic Research-Chinese Academy of Science,Shanghai Branch(No.JCYJ-SHFY-2022–002);Shang-hai Government(No.20JC1415100);The authors would like to thank the synchrotron beamline RIKEN BL44B2(No.2023A1294)at SPring-8 for the beamtime allocation;Kenichi Kato is acknowl-edged for support during synchrotron experiments at BL44B2;This work also acknowledged the Shanghai Technical Service Center of Science and Engineering Computing,Shanghai University.

摘　　要：Element doping is a widely employed strategy to enhance the thermoelectric(TE)properties of various materials.β-FeSi_(2)is a promising low-cost high-temperature TE material with exceptional thermal stabil-ity;however,the doping limit ofβ-FeSi_(2)is usually very low,which limits the tunability of electrical and thermal properties.Recently,a high doping content of 0.16 inβ-FeSi_(2)has been achieved by the introduc-tion of iridium(Ir),leading to the highest reported figure of merit(zT)of 0.6 inβ-FeSi_(2).Motivated by the successful heavy doping with Ir,this work aims to explore element heavy doping inβ-FeSi_(2)with cobalt(Co),a cheaper,more readily available dopant with a smaller atomic radius and closer electronegativity to iron(Fe).In this study,we successfully obtained a record-high doping content of 0.24 in Co-dopedβ-FeSi_(2)through a prolonged annealing process.Despite the absence of a substantial enhancement in the zT of Co-dopedβ-FeSi_(2)at high doping levels,with a maximum zT of 0.3 at 900 K in Fe_(0.92)Co_(0.08)Si_(2),we observed a transition in the carrier transport mechanism as a function of Co doping content,attributed to changes in the band structure.At a low Co doping content(x≤0.12),Fe1-x Cox Si_(2)demonstrates dominant carrier transport via impurity levels within the band gap,exhibiting hopping conduction.As the Co dop-ing content increases(x>0.16),the impurity levels overlap and form an impurity band,and the carrier transport turns into the impurity band conduction.The observed band conduction behavior of Fe1-x Cox Si_(2)(x>0.16)mirrors that of Ir-dopedβ-FeSi_(2),but Fe1-x Cox Si_(2)shows much lower mobility,which can be at-tributed to the localized feature of the impurity band introduced by the Co doping.Overall,this study provides insights into the heavy Co doping and its influence on the TE properties and carrier conduction mechanisms inβ-FeSi_(2),helpful for the further development of this TE system.

关 键 词：β-FeSi_(2) Heavy doping HOPPING Band conduction 

分 类 号：TB33[一般工业技术—材料科学与工程]