We have systematically studied the thermoelectric properties in Zn-doped Sn Te.Strikingly,band convergence and embedded precipitates arising from Zn doping,can trigger a prominent improvement of thermoelectric perform...We have systematically studied the thermoelectric properties in Zn-doped Sn Te.Strikingly,band convergence and embedded precipitates arising from Zn doping,can trigger a prominent improvement of thermoelectric performance.In particular,the value of dimensionless figure of merit z T has increased by 100% and up to ～ 0.5 at 775 K for the optimal sample with 2% Zn content.Present findings demonstrate that carrier concentration and effective mass play crucial roles on the Seebeck coefficient and power factor.The obvious deviation from the Pisarenko line（Seebeck coefficient versus carrier concentration） due to Zn-doping reveals the convergence of valence bands.When the doping concentration exceeds the solubility,precipitates occur and lead to a reduction of lattice thermal conductivity.In addition,bipolar conduction is suppressed,indicating an enlargement of band gap.The Zn-doped Sn Te is shown to be a promising candidate for thermoelectric applications.展开更多
Semiconducting cubic group IV monotellurides,including PbTe and SnTe, have historically led most of the advancements in thermoelectrics. Recently, noncubic ones such as GeTe and MnTe have also shown to be promising,wh...Semiconducting cubic group IV monotellurides,including PbTe and SnTe, have historically led most of the advancements in thermoelectrics. Recently, noncubic ones such as GeTe and MnTe have also shown to be promising,which motivates the current work focusing on the thermoelectric properties of MnGeTe2, a derivative compound of noncubic GeTe and MnTe but crystalizing in a cubic structure.This compound intrinsically comes with a carrier concentration as high as ~3.6×1021 cm-3, indicating the existence of highconcentration cation vacancies due to Ge-precipitation. This intrinsic carrier concentration is much higher than that needed for thermoelectric applications but can be successfully decreased to ~9×1020 cm-3 for MnGe0.9Bi0.1Te2 at room temperature. Such a broad carrier concentration not only offers a full assessment of its electronic transport properties according to a single parabolic band model with acoustic scattering, but also enables an optimization for thermoelectric power factor.The low lattice thermal conductivity of ~1.2 W m-1 K-1 or lower in the entire temperature range, can be understood by the highly disordered cations and cation vacancies. A peak zT approaching 1.0 at 850 K was achieved in materials at an optimal carrier concentration of ~9×1020 cm-3, an isotropic cubic structure as well as a Vickers hardness of >200 HV, strongly indicating MnGeTe2 as a promising thermoelectric material.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.51771126)the Youth Foundation of Science&Technology Department of Sichuan Province,China(Grant No.2016JQ0051)+3 种基金the Sichuan University Talent Introduction Research Funding(Grand No.YJ201537)the Sichuan University Outstanding Young Scholars Research Funding(Grant No.2015SCU04A20)the World First-Class University Construction Fundingthe Fundamental and Frontier Research in Chongqing(Grant No.CSTC2015JCYJBX0026)
文摘We have systematically studied the thermoelectric properties in Zn-doped Sn Te.Strikingly,band convergence and embedded precipitates arising from Zn doping,can trigger a prominent improvement of thermoelectric performance.In particular,the value of dimensionless figure of merit z T has increased by 100% and up to ～ 0.5 at 775 K for the optimal sample with 2% Zn content.Present findings demonstrate that carrier concentration and effective mass play crucial roles on the Seebeck coefficient and power factor.The obvious deviation from the Pisarenko line（Seebeck coefficient versus carrier concentration） due to Zn-doping reveals the convergence of valence bands.When the doping concentration exceeds the solubility,precipitates occur and lead to a reduction of lattice thermal conductivity.In addition,bipolar conduction is suppressed,indicating an enlargement of band gap.The Zn-doped Sn Te is shown to be a promising candidate for thermoelectric applications.
基金supported by the National Natural Science Foundation of China (11474219 and 51772215)the National Key Research and Development Program of China (2018YFB0703600)+3 种基金the Fundamental Research Funds for Science and Technology Innovation Plan of Shanghai (18JC1414600)Fok Ying Tung Education Foundation (20170072210001)"Shu Guang" Project Supported by Shanghai Municipal Education CommissionShanghai Education Development Foundation
文摘Semiconducting cubic group IV monotellurides,including PbTe and SnTe, have historically led most of the advancements in thermoelectrics. Recently, noncubic ones such as GeTe and MnTe have also shown to be promising,which motivates the current work focusing on the thermoelectric properties of MnGeTe2, a derivative compound of noncubic GeTe and MnTe but crystalizing in a cubic structure.This compound intrinsically comes with a carrier concentration as high as ~3.6×1021 cm-3, indicating the existence of highconcentration cation vacancies due to Ge-precipitation. This intrinsic carrier concentration is much higher than that needed for thermoelectric applications but can be successfully decreased to ~9×1020 cm-3 for MnGe0.9Bi0.1Te2 at room temperature. Such a broad carrier concentration not only offers a full assessment of its electronic transport properties according to a single parabolic band model with acoustic scattering, but also enables an optimization for thermoelectric power factor.The low lattice thermal conductivity of ~1.2 W m-1 K-1 or lower in the entire temperature range, can be understood by the highly disordered cations and cation vacancies. A peak zT approaching 1.0 at 850 K was achieved in materials at an optimal carrier concentration of ~9×1020 cm-3, an isotropic cubic structure as well as a Vickers hardness of >200 HV, strongly indicating MnGeTe2 as a promising thermoelectric material.
