| Thermoelectric(TE)materials have received significant attention in waste heat recovery and static state refrigeration,which is favorable to relieve the stress from energy crisis and environmental pollution.The conversion efficiency of thermoelectric materials is primarily determined by ZT-S2?T/?,where S,?,T and? are the Seebeck coefficient,electrical conductivity,absolute temperature and thermal conductivity,respectively.In addition to the high TE performance,the TE materials without expensive,toxic and rare components are more attractive to realize the large-scale practical applications.Recently,chalcogenides have been considered as promising TE materials due to the advantages of low toxicity,low cost and high earth abundance.Cu3SbS4-based materials are composed of nontoxic,low-cost and earth-abundant elements potentially,and exhibit favorable thermoelectric performance.However,some key transport parameters and the thermal stability have not been reported.In this work,the effects of element doping on thermoelectric properties and the thermal stability of Cu3SbS4 were studied.The research contents are listed as follow.1.The effects of Bi doping on thermoelectric transport properties of Cu3SbS4.Bi doping can increase the carrier concentration and enhance the electrical properties to a certain extent.The Bi-doped Cu3SbS4 samples exhibited an effective mass of?3.0 me.Initially,the Fermi level was located at bandgap,and then slightly shift to valance band maximum with the increasing Bi contents.The thermal conductivity of Cu3Sb1-xBixS4 samples was 1.54?2.01 Wm-1K-1 at room temperature,and decreased with increased temperature.The lattice thermal conductivity was dominant,because that the electrical thermal conductivity was less than 5%.Cu3Sb1-xBixS4(x=0.06)sample exhibited the highest power factor with the maximum value of 558 ?Wm-1K-2 at 523K.the maximum ZT of 0.42 was obtained at 623 K for Cu3Sb1-xBixS4(x=0.06)sample.2.The effects of Bi and Sn co-doping on thermoelectric transport properties of Cs3SbS4.Bi and Sn doping can effectively tune the electrical properties and the electronic band structure.The Bi and Sn doping leaded to an increased carrier concentration from 6.4×1017 cm-3 to 7.4×1020 cm-3 and a decreased optical band gap from 0.85 eV to 0.73 eV.The effective mass was increased from?3.0 me for Bi doped samples to?4.0 me for Bi+Sn co-doped samples.An enhanced power factor of 1398?Wm-1K-2 at 623 K was obtained for Cu3Sb1-x-yBixSnyS4(x=0.06,y=0.09).The elastic properties measurements exhibited a large Gruneisen parameter(??2)for Cu3SbS4-based materials.A maximum ZT of 0.76±0.02 at 623 K was achieved for Cu3Sb1-x-yBixSnyS4(x=0.06,y=0.05)sample.The temperature range of 300K-623K was obtained to be thermal stable for Cu3SbS4 materials after the measurements of thermal analysis,thermal treatment in air and heating-cooling circles of TE properties measurements.In addition,Cu3SbS4 materials possess excellent thermal stability after thermal treatment in vacuum at 573 K for totally 500 h and dozens of heating-cooling thermal cycles(300 K?623 K?300 K).3.The comparison of doping effects for Bi,Sn,In and Al doped Cu3SbS4 samples.The Sn-doped sample exhibited the highest power factor and the maximum value of 985 ?Wm-1K-2 was obtained at 623K.The In-doped sample exhibited the lowest power factor.The maximum ZT value of 0.76,0.39 and 0.38 were achieved for Sn,In and Al doped Cu3SbS4 samples.The thermal conductivity decreased with increasing temperature due to the distinct reduced of lattice thermal conductivity.From the perspective of enhancing the electrical properties of Cu3SbS4 materials,the doping effects decreased from Sn,Bi,Al to In. |
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