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
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 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 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
The electronegative filling in skutterudites not only broadened the scope of filling atoms,but also facilitated the preparation of p-type skutterudites.However,the introduction of a single sulfur atom in the Co_(4)Sb_...The electronegative filling in skutterudites not only broadened the scope of filling atoms,but also facilitated the preparation of p-type skutterudites.However,the introduction of a single sulfur atom in the Co_(4)Sb_(12) cannot be achieved without charge compensation through the traditional equilibrium method.In the present study,the dual occupations of S-atoms by self-charge compensation were shown as the most stable forms under high pressure,and a series of p-type S_(y)Co_(4)Sb_(12-2y)S_(2y) skutterudites was successfully prepared by high-pressure-high-temperature(HPHT)method.The electronic structures and transport properties of as-obtained materials were investigated,and the related mechanisms were explored.The results suggested that the presence of S-impurities led to flattening of the electronic band that led to a higher Seebeck coefficient.The S-doped Co_(4)Sb_(12) displayed lower elastic modulus,elastic constant,and Debye temperature,thus indicating the chemical bond softening in skutterudites.The thermal conductivities of S_(y)Co_(4)Sb_(12-2y)S_(2y) compounds reduced monotonously with the increase in Scontent.This study provides a new and promising avenue for optimizing the thermoelectric properties of p-type Co_(4)Sb_(12).展开更多
CoSb3-based mark mid-temperature skutterudites have been a benchthermoelectric material under intensive experimental and theoretical studies for decades. Doping and filling, to the first order, alter the crystal latti...CoSb3-based mark mid-temperature skutterudites have been a benchthermoelectric material under intensive experimental and theoretical studies for decades. Doping and filling, to the first order, alter the crystal lattice constant of CoSb3 in the context of ＂chemical pressure.＂ In this work, we employed ab initio density functional theory in conjunction with semiclassical Boltzmann transport theory to investigate the mechanical properties and especially how hydrostatic loadings, i.e., ＂physical pressure,＂ impact the electronic band structure, Seebeck coefficient, and power factor of pristine CoSb3. It is found that hydrostatic pressure enlarges the band gap, suppresses the density of states （DOS） near the valence band edge, and fosters the band convergence between the valley bands and the conduction band minimum （CBM）. By contrast, hydrostatic tensile reduces the band gap, increases the DOS near the valence band edge, and diminishes the valley bands near the CBM. Therefore, applying hydrostatic pressure provides an alternative avenue for achieving band convergence to improve thermoelectric properties of N-type CoSb3, which is further supported by our carrier concentration studies. These results provide valuable insight into the further improvement of thermoelectric performance of CoSb3-based skutterudites via a synergy of physical and chemical pressures.展开更多
The n-type filled and doped skutterudites Ga_(x)Co_(4)Sb_(12.3) and Ga_(0.2)Co_(4)Sb_(11.3)Te composites with the welldistributed GaSb nanoinclusions are synthesized through the manipulating of metastable Ga fillers a...The n-type filled and doped skutterudites Ga_(x)Co_(4)Sb_(12.3) and Ga_(0.2)Co_(4)Sb_(11.3)Te composites with the welldistributed GaSb nanoinclusions are synthesized through the manipulating of metastable Ga fillers and enrichment of Sb by an in-situ method with a proper annealing procedure.Ga atoms can fill the icosahedron cages of skutterudite at high temperature,but at low temperature,they are driven out from the lattice voids and form the second phase of GaSb at grain boundaries.The presence of GaSb second phases reduces the thermal conductivity effectively.Te doping leads to a significant increase in carrier concentration of Ga_(0.2)Co_(4)Sb_(11.3)Te,thus largely suppresses the bipolar effect of Ga_(x)Co_(4)Sb_(12.3),resulting in a great enhancement in power factor.Moreover,Te doping induces mass and strain fluctuation,which decreases the lattice thermal conductivity further.Consequently,the maximum ZT is increased from 0.56 for Ga_(0.2)Co_(4)Sb_(12.3) at 573 K to 1.48 for Ga_(0.2)Co_(4)Sb_(11.3)Te at 873 K,which is advantageous to improve the thermoelectric conversion efficiency for commercial application.展开更多
To achieve a better material for thermoelectric power generation device, filled skutterudite Yb0.3 Co_4 Sb_(12) samples were fabricated by melting-quenching-annealing-spark plasma sintering(SPS)method. Two sets of sam...To achieve a better material for thermoelectric power generation device, filled skutterudite Yb0.3 Co_4 Sb_(12) samples were fabricated by melting-quenching-annealing-spark plasma sintering(SPS)method. Two sets of samples, before and after SPS, were investigated. In both the two sets of samples,the average grain size of the samples increases monotonously with the increase of annealing time,while Yb filling fraction firstly increases and then decreases. Yb not filling into the skutterudite remains at the grain boundaries in the form of Yb_2 O_3 after SPS, which could be quantified by the spatially difference method of energy dispersive spectra. Step distribution of Yb filling fraction was observed in the samples annealed for 1 h, which was caused by the microstructural evolution from the peritectic phases to the skutterudite phase. The sample annealed for 3 days and SPS sintered possesses the maximum value of Yb filling fraction 0.249 and the maximum ZT value of 1.24 at 850 K. These results are helpful to better understand the microstructural evolution and Yb filling behavior in skutterudite materials.展开更多
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 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.
基金the financial support from the National Natural Science Foundation of China(Grant No.51772231 and 51972253)the Fundamental Research Funds for the Central Universities(WUT:2017-YB-033,2020IB001,and 2020IB013).
文摘The electronegative filling in skutterudites not only broadened the scope of filling atoms,but also facilitated the preparation of p-type skutterudites.However,the introduction of a single sulfur atom in the Co_(4)Sb_(12) cannot be achieved without charge compensation through the traditional equilibrium method.In the present study,the dual occupations of S-atoms by self-charge compensation were shown as the most stable forms under high pressure,and a series of p-type S_(y)Co_(4)Sb_(12-2y)S_(2y) skutterudites was successfully prepared by high-pressure-high-temperature(HPHT)method.The electronic structures and transport properties of as-obtained materials were investigated,and the related mechanisms were explored.The results suggested that the presence of S-impurities led to flattening of the electronic band that led to a higher Seebeck coefficient.The S-doped Co_(4)Sb_(12) displayed lower elastic modulus,elastic constant,and Debye temperature,thus indicating the chemical bond softening in skutterudites.The thermal conductivities of S_(y)Co_(4)Sb_(12-2y)S_(2y) compounds reduced monotonously with the increase in Scontent.This study provides a new and promising avenue for optimizing the thermoelectric properties of p-type Co_(4)Sb_(12).
基金supported by the Office of Science of the US Department of Energy (Nos. DEAC05-00OR22750 and DE-AC02-05-CH11231)the support of National Science Foundation (No. DMR-1307740)
文摘CoSb3-based mark mid-temperature skutterudites have been a benchthermoelectric material under intensive experimental and theoretical studies for decades. Doping and filling, to the first order, alter the crystal lattice constant of CoSb3 in the context of ＂chemical pressure.＂ In this work, we employed ab initio density functional theory in conjunction with semiclassical Boltzmann transport theory to investigate the mechanical properties and especially how hydrostatic loadings, i.e., ＂physical pressure,＂ impact the electronic band structure, Seebeck coefficient, and power factor of pristine CoSb3. It is found that hydrostatic pressure enlarges the band gap, suppresses the density of states （DOS） near the valence band edge, and fosters the band convergence between the valley bands and the conduction band minimum （CBM）. By contrast, hydrostatic tensile reduces the band gap, increases the DOS near the valence band edge, and diminishes the valley bands near the CBM. Therefore, applying hydrostatic pressure provides an alternative avenue for achieving band convergence to improve thermoelectric properties of N-type CoSb3, which is further supported by our carrier concentration studies. These results provide valuable insight into the further improvement of thermoelectric performance of CoSb3-based skutterudites via a synergy of physical and chemical pressures.
基金supported by the National Natural Science Foundation of China(Nos.61604031,51672037 and 61727818)the subproject of the National Key and Development Program of China(No.2017YFC0602102)the Department of Science and Technology of Sichuan Province(No.2019YFH0009).
文摘The n-type filled and doped skutterudites Ga_(x)Co_(4)Sb_(12.3) and Ga_(0.2)Co_(4)Sb_(11.3)Te composites with the welldistributed GaSb nanoinclusions are synthesized through the manipulating of metastable Ga fillers and enrichment of Sb by an in-situ method with a proper annealing procedure.Ga atoms can fill the icosahedron cages of skutterudite at high temperature,but at low temperature,they are driven out from the lattice voids and form the second phase of GaSb at grain boundaries.The presence of GaSb second phases reduces the thermal conductivity effectively.Te doping leads to a significant increase in carrier concentration of Ga_(0.2)Co_(4)Sb_(11.3)Te,thus largely suppresses the bipolar effect of Ga_(x)Co_(4)Sb_(12.3),resulting in a great enhancement in power factor.Moreover,Te doping induces mass and strain fluctuation,which decreases the lattice thermal conductivity further.Consequently,the maximum ZT is increased from 0.56 for Ga_(0.2)Co_(4)Sb_(12.3) at 573 K to 1.48 for Ga_(0.2)Co_(4)Sb_(11.3)Te at 873 K,which is advantageous to improve the thermoelectric conversion efficiency for commercial application.
基金financially supported by the National Natural Science Foundation of China under Grant Nos. 51532006 and 11704238Shanghai Municipal Science and Technology Commission of Shanghai Municipality under Grant No. 16DZ2260601State Administration of Foreign Experts Affairs of China 111 Project under Grant No. D16002
文摘To achieve a better material for thermoelectric power generation device, filled skutterudite Yb0.3 Co_4 Sb_(12) samples were fabricated by melting-quenching-annealing-spark plasma sintering(SPS)method. Two sets of samples, before and after SPS, were investigated. In both the two sets of samples,the average grain size of the samples increases monotonously with the increase of annealing time,while Yb filling fraction firstly increases and then decreases. Yb not filling into the skutterudite remains at the grain boundaries in the form of Yb_2 O_3 after SPS, which could be quantified by the spatially difference method of energy dispersive spectra. Step distribution of Yb filling fraction was observed in the samples annealed for 1 h, which was caused by the microstructural evolution from the peritectic phases to the skutterudite phase. The sample annealed for 3 days and SPS sintered possesses the maximum value of Yb filling fraction 0.249 and the maximum ZT value of 1.24 at 850 K. These results are helpful to better understand the microstructural evolution and Yb filling behavior in skutterudite materials.
