Skutterudite CoAs3 is a potentially important thermoelectric material. Morse potential is employed here to carry out molecular dynamics simulations of nanobulk CoAs3 at the temperature of 0 K. The stress-strain relati...Skutterudite CoAs3 is a potentially important thermoelectric material. Morse potential is employed here to carry out molecular dynamics simulations of nanobulk CoAs3 at the temperature of 0 K. The stress-strain relationships under uniaxial tensile and/or compressive strain are obtained. The elastic modulus, extreme strength and deformation mechanism are studied. The simulation results indicate that nanobulk CoAs3 abruptly ruptures at much higher strain level under tension than conventional bulk CoAs3. Both the extreme stresses under tension and compression are much higher than those of conventional bulk CoAs3.展开更多
Polycrystalline samples of Sm partially filled skutterudites SmyFexCo4-xSb12 were prepared by melting and Spark Plasma Sintering technique. The results of Rietveld refinement showed that the obtained SmyFexCo4-xSb12 s...Polycrystalline samples of Sm partially filled skutterudites SmyFexCo4-xSb12 were prepared by melting and Spark Plasma Sintering technique. The results of Rietveld refinement showed that the obtained SmyFexCo4-xSb12 samples possessed filled skutterudite structures. The thermal parameter （B） of Sm is larger than that of Sb, Fe, and Co, indicating that Sm ＂rattled＂ in Sb-icosahedron voids. The effects of filling atom Sm on thermoelectric properties of these compounds were investigated. With the increase of Sm filling fraction （y）, electrical conductivity decreased, Seebeck coefficient increased and had a maximum value when y was 0.38; thermal conductivity reduced and had a minimum value when y was 0. 32. At 750 K, the highest figure of merit of 0.68 was obtained for Sm0.32Fe1.47Co2.53Sb12.展开更多
Nanocomposite is proved to be an effective method to improve thermoelectric performance.In the present study,graphene is introduced into p-type skutterudite La0.8Ti0.1Ga0.1Fe3CoSb12 by plasma-enhanced chemical vapor d...Nanocomposite is proved to be an effective method to improve thermoelectric performance.In the present study,graphene is introduced into p-type skutterudite La0.8Ti0.1Ga0.1Fe3CoSb12 by plasma-enhanced chemical vapor deposition（PECVD）method to form skutterudite/graphene nanocomposites.It is demonstrated that the graphene has no obvious effect on the electrical conductivity of La0.8Ti0.1Ga0.1Fe3CoSb12,but the Seebeck coefficient is slightly improved at high temperature,thereby leading to high power factor.Furthermore,due to the enhancement of phonon scattering by the graphene,the lattice thermal conductivity is reduced significantly.Ultimately,the maximum z T value of La0.8Ti0.1Ga0.1Fe3CoSb12/graphene is higher than that of graphene-free alloy and reaches to 1.0 at 723 K.Such an approach raised by us enriches prospects for future practical application.展开更多
The correlations among composition, structure, chemical bond andthermoelectric property of skutterudites CoSb_3 and CeCo_5Fe_3Sb_12have been studied by using density function and discrete variation(DFT- DVM) method. T...The correlations among composition, structure, chemical bond andthermoelectric property of skutterudites CoSb_3 and CeCo_5Fe_3Sb_12have been studied by using density function and discrete variation(DFT- DVM) method. Three models for this study were proposed andcalculated by which the 'rattling' pattern was Described. Model 1 iswith Ce in the center, model 2 is with Ce away the center and near toSb, and model 3 is Also with Ce away the center but near to Fe. Thecalculated results show that in model 3, the ionic bond is theStrongest, but the covalent bond is the weakest.展开更多
The binary CoSb_(3) skutterudite thermoelectric material has high thermal conductivity due to the covalent bond between Co and Sb, and the thermoelectric figure of merit, ZT, is very low. The thermal conductivity of C...The binary CoSb_(3) skutterudite thermoelectric material has high thermal conductivity due to the covalent bond between Co and Sb, and the thermoelectric figure of merit, ZT, is very low. The thermal conductivity of CoSb_(3) materials can be significantly reduced through phonon engineering, such as low-dimensional structure, the introduction of nano second phases,nanointerfaces or nanopores, which greatly improves their ZT values. The phonon engineering can optimize significantly the thermal transport properties of CoSb_(3)-based materials. However, the improvement of the electronic transport properties is not obvious, or even worse. Energy band and charge-carrier engineering can significantly improve the electronic transport properties of CoSb_(3)-based materials while optimizing the thermal transport properties. Therefore, the decoupling of thermal and electronic transport properties of CoSb_(3)-based materials can be realized by energy band and charge-carrier engineering. This review summarizes some methods of optimizing synergistically the electronic and thermal transport properties of CoSb_(3) materials through the energy band and charge-carrier engineering strategies. Energy band engineering strategies include band convergence or resonant energy levels caused by doping/filling. The charge-carrier engineering strategy includes the optimization of carrier concentration and mobility caused by doping/filling, forming modulation doped structures or introducing nano second phase. These strategies are effective means to improve performance of thermoelectric materials and provide new research ideas of development of high-efficiency thermoelectric materials.展开更多
We report the synthesis of Nd-filled and Fe substituted p-type Ndx Fe（3.2）Co（0.8）Fe（3.2）Co（0.8）Sb（12）（x=0.5,0.6,0.7,0.8,and 0.9）skutterudites by the solid-state reaction method.The influences of Nd filler ...We report the synthesis of Nd-filled and Fe substituted p-type Ndx Fe（3.2）Co（0.8）Fe（3.2）Co（0.8）Sb（12）（x=0.5,0.6,0.7,0.8,and 0.9）skutterudites by the solid-state reaction method.The influences of Nd filler on the electrical and thermal transport prop-erties are investigated in a temperature range from room temperature to 850 K.A lowest lattice thermal conductivity of 0.88 W·m^-1·K^-1 is obtained in Nd0.8Fe（3.2）Co（0.8）Fe（3.2）Co（0.8）Sb（12）at 673 K,which results from the localized vibration modes of fillers and the increase of grains boundaries.Meanwhile,the maximum power factor is 2.77 m W·m^-1·K^-2 for the Nd（0.9）Fe（3.2）Co（0.8）Fe（3.2）Co（0.8）Sb（12）sample at 668 K.Overall,the highest dimensionless figure of merit z T=0.87 is achieved at 714 Kfor Nd（0.9）Fe（3.2）Co（0.8）Fe（3.2）Co（0.8）Sb（12）.展开更多
The enhancements in thermoelectric(TE)performances of p-type skutterudites are usually limited due to the relatively low Seebeck coefficients owing to the higher carrier concentration and more impurity phases induced ...The enhancements in thermoelectric(TE)performances of p-type skutterudites are usually limited due to the relatively low Seebeck coefficients owing to the higher carrier concentration and more impurity phases induced by inherent structural instability of a Fe-based skutterudite.As shown in this study,alloying engineering of Ni doping at Fe sites in a p-type CeFe_(3.8)Co_(0.2)Sb_(12)skutterudite can not only reduce the impurity phases with high thermal conductivity but also regulate the carrier concentration,and thus significantly increase the Seebeck coefficient.The thermal conductivity was largely suppressed due to the enhanced point defect phonon scattering and decreased hole concentration.As a result,a TE figure of merit ZT of the CeFe_(3.5)Ni_(0.3)Co_(0.2)Sb_(12)sample reached 0.8,which is approximately 50%higher than that of a Ni-free sample.Appropriate Ni doping can maintain a high ZT at a high temperature by controlling the reduction in a band gap.Therefore,a high average ZT close to 0.8 at 650–800 K for CeFe_(3.5)Ni_(0.3)Co_(0.2)Sb_(12)was obtained,which was comparable to or even higher than those of the reported Ce-filled Fe-based skutterudites due to the synergistic optimization of electrical and thermal performances.This study provides a strategy to synergistically optimize electrical–thermal performances of the p-type skutterudites by alloying engineering.展开更多
The great pressure of energy shortage has made CoSb_(3) materials with excellent mechanical stability in the mid-temperature region favored for the integration of thermoelectric devices.However,their ex-cessive lattic...The great pressure of energy shortage has made CoSb_(3) materials with excellent mechanical stability in the mid-temperature region favored for the integration of thermoelectric devices.However,their ex-cessive lattice thermal conductivity and poor Seebeck coefficient lead to low energy conversion effi-ciency.Filling Yb into the lattice void to optimize the band structure and regulate the chemical po-tential is an indispensable means for improving the thermoelectric properties of CoSb_(3)-based materials,while the phase structure and thermoelectric properties vary with the preparation process.This motivates the current work to focus on the influence of annealing temperature on the microstructure and thermoelectric properties of Yb-filled CoSb_(3).Experimental analysis and theoretical model eluci-dated that an increase in annealing temperature can optimize the Yb filling fraction,which simulta-neously manipulates the band structure as well as chemical potential,resulting in an excellent electrical property.Furthermore,the phase and microstructure characterization clarify that the annealing temperature can effectively affect the grain size.The complex grain boundary induced by grain refinement,more filled Yb atoms and precipitates strongly scatter wide-frequency phonons,significantly suppressing the lattice thermal conductivity.As a result,a superior dimensionless figure of merit(ZT)value of~1.33 at 823 K and an average ZTave of~0.9(323-823 K)were achieved in the Ybo.4Co4Sb12 sample annealed at 923 K,and the calculated conversion efficiency could reach~13%.This work pro-vides a unique paradigm to improve thermoelectrics in the filled CoSb_(3)-based skutterudites by annealing engineering.展开更多
基金Funded by 973 Program(No.2007CB607506)the National Natural Science Foundation of China(No.10672127)the Ministryof Education of China(No.NCET-04-0725)
文摘Skutterudite CoAs3 is a potentially important thermoelectric material. Morse potential is employed here to carry out molecular dynamics simulations of nanobulk CoAs3 at the temperature of 0 K. The stress-strain relationships under uniaxial tensile and/or compressive strain are obtained. The elastic modulus, extreme strength and deformation mechanism are studied. The simulation results indicate that nanobulk CoAs3 abruptly ruptures at much higher strain level under tension than conventional bulk CoAs3. Both the extreme stresses under tension and compression are much higher than those of conventional bulk CoAs3.
基金supported by the National Basic Research Program of China (No. 2007CB607502)the Key Program of National Natural Science Foundation of China (No. 50731006)
基金Project supported by the National Natural Science Foundation of China (50372049)the Major International Cooperation Program of the National Natural Science Foundation of China (50310353)
文摘Polycrystalline samples of Sm partially filled skutterudites SmyFexCo4-xSb12 were prepared by melting and Spark Plasma Sintering technique. The results of Rietveld refinement showed that the obtained SmyFexCo4-xSb12 samples possessed filled skutterudite structures. The thermal parameter （B） of Sm is larger than that of Sb, Fe, and Co, indicating that Sm ＂rattled＂ in Sb-icosahedron voids. The effects of filling atom Sm on thermoelectric properties of these compounds were investigated. With the increase of Sm filling fraction （y）, electrical conductivity decreased, Seebeck coefficient increased and had a maximum value when y was 0.38; thermal conductivity reduced and had a minimum value when y was 0. 32. At 750 K, the highest figure of merit of 0.68 was obtained for Sm0.32Fe1.47Co2.53Sb12.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51622101,51771065,and 51471061)
文摘Nanocomposite is proved to be an effective method to improve thermoelectric performance.In the present study,graphene is introduced into p-type skutterudite La0.8Ti0.1Ga0.1Fe3CoSb12 by plasma-enhanced chemical vapor deposition（PECVD）method to form skutterudite/graphene nanocomposites.It is demonstrated that the graphene has no obvious effect on the electrical conductivity of La0.8Ti0.1Ga0.1Fe3CoSb12,but the Seebeck coefficient is slightly improved at high temperature,thereby leading to high power factor.Furthermore,due to the enhancement of phonon scattering by the graphene,the lattice thermal conductivity is reduced significantly.Ultimately,the maximum z T value of La0.8Ti0.1Ga0.1Fe3CoSb12/graphene is higher than that of graphene-free alloy and reaches to 1.0 at 723 K.Such an approach raised by us enriches prospects for future practical application.
基金Funded by the Open Foundation of State Key of Lab.Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology,and Science Foundation of Hubei Province(No. 98J028)
文摘The correlations among composition, structure, chemical bond andthermoelectric property of skutterudites CoSb_3 and CeCo_5Fe_3Sb_12have been studied by using density function and discrete variation(DFT- DVM) method. Three models for this study were proposed andcalculated by which the 'rattling' pattern was Described. Model 1 iswith Ce in the center, model 2 is with Ce away the center and near toSb, and model 3 is Also with Ce away the center but near to Fe. Thecalculated results show that in model 3, the ionic bond is theStrongest, but the covalent bond is the weakest.
基金supported by the National Natural Science Foundation of China (Grant No. 51872006)the Excellent Youth Project of Natural Science Foundation of Anhui Province of China (Grant No. 2208085Y17)。
文摘The binary CoSb_(3) skutterudite thermoelectric material has high thermal conductivity due to the covalent bond between Co and Sb, and the thermoelectric figure of merit, ZT, is very low. The thermal conductivity of CoSb_(3) materials can be significantly reduced through phonon engineering, such as low-dimensional structure, the introduction of nano second phases,nanointerfaces or nanopores, which greatly improves their ZT values. The phonon engineering can optimize significantly the thermal transport properties of CoSb_(3)-based materials. However, the improvement of the electronic transport properties is not obvious, or even worse. Energy band and charge-carrier engineering can significantly improve the electronic transport properties of CoSb_(3)-based materials while optimizing the thermal transport properties. Therefore, the decoupling of thermal and electronic transport properties of CoSb_(3)-based materials can be realized by energy band and charge-carrier engineering. This review summarizes some methods of optimizing synergistically the electronic and thermal transport properties of CoSb_(3) materials through the energy band and charge-carrier engineering strategies. Energy band engineering strategies include band convergence or resonant energy levels caused by doping/filling. The charge-carrier engineering strategy includes the optimization of carrier concentration and mobility caused by doping/filling, forming modulation doped structures or introducing nano second phase. These strategies are effective means to improve performance of thermoelectric materials and provide new research ideas of development of high-efficiency thermoelectric materials.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674040,11404044,51472036,51672270,and 51401202)the Fundamental Research Funds for the Central Universities(Grant No.106112016CDJZR308808)+1 种基金the 100 Talent Program of the Chinese Academy of Sciences(Grant No.2013-46)the Project for Fundamental and Frontier Research in Chongqing,China(Grant No.CSTC2015JCYJBX0026)
文摘We report the synthesis of Nd-filled and Fe substituted p-type Ndx Fe（3.2）Co（0.8）Fe（3.2）Co（0.8）Sb（12）（x=0.5,0.6,0.7,0.8,and 0.9）skutterudites by the solid-state reaction method.The influences of Nd filler on the electrical and thermal transport prop-erties are investigated in a temperature range from room temperature to 850 K.A lowest lattice thermal conductivity of 0.88 W·m^-1·K^-1 is obtained in Nd0.8Fe（3.2）Co（0.8）Fe（3.2）Co（0.8）Sb（12）at 673 K,which results from the localized vibration modes of fillers and the increase of grains boundaries.Meanwhile,the maximum power factor is 2.77 m W·m^-1·K^-2 for the Nd（0.9）Fe（3.2）Co（0.8）Fe（3.2）Co（0.8）Sb（12）sample at 668 K.Overall,the highest dimensionless figure of merit z T=0.87 is achieved at 714 Kfor Nd（0.9）Fe（3.2）Co（0.8）Fe（3.2）Co（0.8）Sb（12）.
基金supported by the National Natural Science Foundation of China(Grant Nos.51872006,and 22273081)and Anhui Province Natural Science Foundation for Excellent Youth Scholars(Grant No.2208085Y17).
文摘The enhancements in thermoelectric(TE)performances of p-type skutterudites are usually limited due to the relatively low Seebeck coefficients owing to the higher carrier concentration and more impurity phases induced by inherent structural instability of a Fe-based skutterudite.As shown in this study,alloying engineering of Ni doping at Fe sites in a p-type CeFe_(3.8)Co_(0.2)Sb_(12)skutterudite can not only reduce the impurity phases with high thermal conductivity but also regulate the carrier concentration,and thus significantly increase the Seebeck coefficient.The thermal conductivity was largely suppressed due to the enhanced point defect phonon scattering and decreased hole concentration.As a result,a TE figure of merit ZT of the CeFe_(3.5)Ni_(0.3)Co_(0.2)Sb_(12)sample reached 0.8,which is approximately 50%higher than that of a Ni-free sample.Appropriate Ni doping can maintain a high ZT at a high temperature by controlling the reduction in a band gap.Therefore,a high average ZT close to 0.8 at 650–800 K for CeFe_(3.5)Ni_(0.3)Co_(0.2)Sb_(12)was obtained,which was comparable to or even higher than those of the reported Ce-filled Fe-based skutterudites due to the synergistic optimization of electrical and thermal performances.This study provides a strategy to synergistically optimize electrical–thermal performances of the p-type skutterudites by alloying engineering.
基金supported by the National Key Research and Development Program of China (Grant Nos.2018YFA0702100 and 2022YFB3803900)the Joint Funds of the National Natural Science Foundation of China and the Chinese Academy of Sciences (CAS)’Large-Scale Scientific Facility (Grant No.U1932106)the Sichuan University Innovation Research Pro-gram of China (Grant No.2020SCUNL112).
文摘The great pressure of energy shortage has made CoSb_(3) materials with excellent mechanical stability in the mid-temperature region favored for the integration of thermoelectric devices.However,their ex-cessive lattice thermal conductivity and poor Seebeck coefficient lead to low energy conversion effi-ciency.Filling Yb into the lattice void to optimize the band structure and regulate the chemical po-tential is an indispensable means for improving the thermoelectric properties of CoSb_(3)-based materials,while the phase structure and thermoelectric properties vary with the preparation process.This motivates the current work to focus on the influence of annealing temperature on the microstructure and thermoelectric properties of Yb-filled CoSb_(3).Experimental analysis and theoretical model eluci-dated that an increase in annealing temperature can optimize the Yb filling fraction,which simulta-neously manipulates the band structure as well as chemical potential,resulting in an excellent electrical property.Furthermore,the phase and microstructure characterization clarify that the annealing temperature can effectively affect the grain size.The complex grain boundary induced by grain refinement,more filled Yb atoms and precipitates strongly scatter wide-frequency phonons,significantly suppressing the lattice thermal conductivity.As a result,a superior dimensionless figure of merit(ZT)value of~1.33 at 823 K and an average ZTave of~0.9(323-823 K)were achieved in the Ybo.4Co4Sb12 sample annealed at 923 K,and the calculated conversion efficiency could reach~13%.This work pro-vides a unique paradigm to improve thermoelectrics in the filled CoSb_(3)-based skutterudites by annealing engineering.
