The synergistic cooling of thermoelectromagnetic materials promises a breakthrough in the efficiency of single refrigeration and has attracted extensive research.The study of heterogeneous interface is crucial for ach...The synergistic cooling of thermoelectromagnetic materials promises a breakthrough in the efficiency of single refrigeration and has attracted extensive research.The study of heterogeneous interface is crucial for achieving the synergistic performance of both materials.In this work,a composite material comprising Bi_(2)Te_(3)-based thermoelectric material and MnCoGe-based magnetocaloric material is synthesized,which is a material exhibiting both thermoelectric and magnetocaloric properties.During the plasma-activated sintering process of the composite material,elemental interdiffusion of Mn,Co,Sb,and Te occurs,forming a diffusion layer of MnTe and CoSbTe.Reaction of heterogeneous interface leads to point defects within the material,significantly increasing the carrier concentration.Optimization of the sintering temperature results in a thermoelectric figure of merit(ZT)of 0.69 at 300 K and−ΔS_(max) of 0.97 J kg^(−1) K^(−1) at room temperature under a 5 T magnetic field for the Bi_(0.5)Sb_(1.5)Te_(3)/10 wt%Mn_(0.9)Cu_(0.1)CoGe composite sintered at 623 K and under 50 MPa.This study demonstrates that Bi_(0.5)Sb_(1.5)Te_(3)/Mn_(0.9)Cu_(0.1)CoGe is a potential candidate for efficient thermoelectromagnetic cooling applications.展开更多
Materials with both large magnetocaloric response and high thermoelectric performance are of vital importance for all-solid-state thermoelectromagnetic cooling.These two properties,however,hardly coexist in single pha...Materials with both large magnetocaloric response and high thermoelectric performance are of vital importance for all-solid-state thermoelectromagnetic cooling.These two properties,however,hardly coexist in single phase materials except previously reported hexagonal Cr_(1-x)Te half metal where a relatively high magnetic entropy change(-△S_(M))of~2.4 J·kg^(-1)·K^(-1)@5 T and a moderate thermoelectric figure of merit(ZT)of~1.2×10^(-2)@300 K are simultaneously recorded.Herein we aim to increase the thermoelectric performance of Cr_(1-x)Te by compositing with semiconducting Ag_(2)Te.It is discovered that the in-situ synthesis of Cr_(1-x)Te/Ag_(2)Te composites by reacting their constitute elements above melting temperatures is unsuccessful because of strong phase competition.Specifically,at elevated temperatures(T>800 K),Cr_(1-x)Te has a much lower deformation energy than Ag_(2)Te and tends to become more Cr-deficient by capturing Te from Ag_(2)Te.Therefore,Ag is insufficiently reacted and as a metal it deteriorates ZT.We then rationalize the synthesis of Cr_(1-x)Te/Ag_(2)Te composites by ex-situ mix of the pre-prepared Cr_(1-x)Te and Ag_(2)Te binary compounds followed by densification at a low sintering temperature of 573 K under a pressure of 3.5 GPa.We show that by compositing with 7 mol%Ag_(2)Te,the Seebeck coefficient of Cr_(1-x)Te is largely increased while the lattice thermal conductivity is considerably reduced,leading to 72%improvement of ZT.By comparison,-△S_(M)is only slightly reduced by 10%in the composite.Our work demonstrates the potential of Cr_(1-x)Te/Ag_(2)Te composites for thermoelectromagnetic cooling.展开更多
Sn-3wt%Pb alloy was directionally solidified without and with a 0.08T transverse magnetic field(TMF),and real-time recorded by in-situ synchrotron X-ray imaging.Results indicate that TMF shortened the distance from th...Sn-3wt%Pb alloy was directionally solidified without and with a 0.08T transverse magnetic field(TMF),and real-time recorded by in-situ synchrotron X-ray imaging.Results indicate that TMF shortened the distance from the location of nucleation to the advancing interface,and accelerated the growth rate of the equiaxed crystal,which caused the columnar-to-equiaxed transition(CET)finally.The thermoelectromagnetic convection(TEMC)in front of the interface and around the crystal’s dendritic branch should respond to changes of the distance and the growth rate.展开更多
In this work binary alloy of Pb-Sn is directionally solidified under transverse,slowly rotating magnetic field.For some alloys during directional solidification in the transverse magnetic field significant macrosegreg...In this work binary alloy of Pb-Sn is directionally solidified under transverse,slowly rotating magnetic field.For some alloys during directional solidification in the transverse magnetic field significant macrosegregation along the diameter of the ingot may appear if the growth velocity and magnetic field strength are chosen appropriately.This occurs as a result of thermoelectric current,driven by the applied temperature gradient at the solidification interface,and magnetic field interaction caused liquid phase forced convection(thermoelectrornagnetic convection). Magnetic field rotation velocity in chosen to be slow enough that induced electric current can be neglected but still fast enough not letting thermoelectromagnetic convection fully develop in the scale of crucible.In this case the effect caused by thermoelectromagnetic convection on the structure is expected to be different from the case with static magnetic field,which is already studied in many works.Newest experimental results as well as theoretical description and interpretation of the obtained results of direction solidification experiments under rotating magnetic field will be presented in this paper.Magnetic field of 0.5 T is created by rotating permanent magnet system driven by electric step motor.展开更多
Synergistically regulating carrier and phonon transport on the nanoscale is extremely difficult for all thermoelectric(TE)materials without cage structures.Herein BaFe_(12)O_(19)/Bi_(2)Te_(2.5)Se_(0.5)thermoelectromag...Synergistically regulating carrier and phonon transport on the nanoscale is extremely difficult for all thermoelectric(TE)materials without cage structures.Herein BaFe_(12)O_(19)/Bi_(2)Te_(2.5)Se_(0.5)thermoelectromagnetic nanocomposites are designed and synthesized as a benchmarking example to simultaneously tailor the transport properties on the nanoscale.A magneto-trapped carrier effect induced by BaFe_(12)O_(19)hard-magnetic nanoparticles(NPs)is discovered,which can lower the carrier concentration of n-type Bi_(2)Te_(2.5)Se_(0.5)matrix by 16%,and increase the Seebeck coefficient by 16%.Meanwhile,BaFe_(12)O_(19)NPs provide phonon scattering centers and reduce the thermal conductivity by 12%.As a result,the ZT value of the nanocomposites is enhanced by more than 25%in the range of 300-450 K,and the cooling temperature difference increases by 65%near room temperature.This work greatly broadens the commercial application potential of ntype Bi_(2)Te_(2.5)Se_(0.5),and demonstrates magneto-trapped carrier effect as a universal strategy to enhance the electro-thermal conversion performance of TE materials with high carrier concentration.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2019YFA0704900)the National Natural Science Foundation of China(Grant No.52171221).
文摘The synergistic cooling of thermoelectromagnetic materials promises a breakthrough in the efficiency of single refrigeration and has attracted extensive research.The study of heterogeneous interface is crucial for achieving the synergistic performance of both materials.In this work,a composite material comprising Bi_(2)Te_(3)-based thermoelectric material and MnCoGe-based magnetocaloric material is synthesized,which is a material exhibiting both thermoelectric and magnetocaloric properties.During the plasma-activated sintering process of the composite material,elemental interdiffusion of Mn,Co,Sb,and Te occurs,forming a diffusion layer of MnTe and CoSbTe.Reaction of heterogeneous interface leads to point defects within the material,significantly increasing the carrier concentration.Optimization of the sintering temperature results in a thermoelectric figure of merit(ZT)of 0.69 at 300 K and−ΔS_(max) of 0.97 J kg^(−1) K^(−1) at room temperature under a 5 T magnetic field for the Bi_(0.5)Sb_(1.5)Te_(3)/10 wt%Mn_(0.9)Cu_(0.1)CoGe composite sintered at 623 K and under 50 MPa.This study demonstrates that Bi_(0.5)Sb_(1.5)Te_(3)/Mn_(0.9)Cu_(0.1)CoGe is a potential candidate for efficient thermoelectromagnetic cooling applications.
基金Project supported by the National Key Research and Development Program of China(Grant No.2019YFA0704900)the National Natural Science Foundation of China(Grant No.52171221)。
文摘Materials with both large magnetocaloric response and high thermoelectric performance are of vital importance for all-solid-state thermoelectromagnetic cooling.These two properties,however,hardly coexist in single phase materials except previously reported hexagonal Cr_(1-x)Te half metal where a relatively high magnetic entropy change(-△S_(M))of~2.4 J·kg^(-1)·K^(-1)@5 T and a moderate thermoelectric figure of merit(ZT)of~1.2×10^(-2)@300 K are simultaneously recorded.Herein we aim to increase the thermoelectric performance of Cr_(1-x)Te by compositing with semiconducting Ag_(2)Te.It is discovered that the in-situ synthesis of Cr_(1-x)Te/Ag_(2)Te composites by reacting their constitute elements above melting temperatures is unsuccessful because of strong phase competition.Specifically,at elevated temperatures(T>800 K),Cr_(1-x)Te has a much lower deformation energy than Ag_(2)Te and tends to become more Cr-deficient by capturing Te from Ag_(2)Te.Therefore,Ag is insufficiently reacted and as a metal it deteriorates ZT.We then rationalize the synthesis of Cr_(1-x)Te/Ag_(2)Te composites by ex-situ mix of the pre-prepared Cr_(1-x)Te and Ag_(2)Te binary compounds followed by densification at a low sintering temperature of 573 K under a pressure of 3.5 GPa.We show that by compositing with 7 mol%Ag_(2)Te,the Seebeck coefficient of Cr_(1-x)Te is largely increased while the lattice thermal conductivity is considerably reduced,leading to 72%improvement of ZT.By comparison,-△S_(M)is only slightly reduced by 10%in the composite.Our work demonstrates the potential of Cr_(1-x)Te/Ag_(2)Te composites for thermoelectromagnetic cooling.
基金Item Sponsored by the CNRS/ANR OPTIMAG projectthe Natural Science Foundation of China (No.50911130365) the National 973 Project (No.2011CB610404)
文摘Sn-3wt%Pb alloy was directionally solidified without and with a 0.08T transverse magnetic field(TMF),and real-time recorded by in-situ synchrotron X-ray imaging.Results indicate that TMF shortened the distance from the location of nucleation to the advancing interface,and accelerated the growth rate of the equiaxed crystal,which caused the columnar-to-equiaxed transition(CET)finally.The thermoelectromagnetic convection(TEMC)in front of the interface and around the crystal’s dendritic branch should respond to changes of the distance and the growth rate.
基金Item Sponsored by ESF project"Support for Doctoral studies at University of Latvia"and French ministry of education
文摘In this work binary alloy of Pb-Sn is directionally solidified under transverse,slowly rotating magnetic field.For some alloys during directional solidification in the transverse magnetic field significant macrosegregation along the diameter of the ingot may appear if the growth velocity and magnetic field strength are chosen appropriately.This occurs as a result of thermoelectric current,driven by the applied temperature gradient at the solidification interface,and magnetic field interaction caused liquid phase forced convection(thermoelectrornagnetic convection). Magnetic field rotation velocity in chosen to be slow enough that induced electric current can be neglected but still fast enough not letting thermoelectromagnetic convection fully develop in the scale of crucible.In this case the effect caused by thermoelectromagnetic convection on the structure is expected to be different from the case with static magnetic field,which is already studied in many works.Newest experimental results as well as theoretical description and interpretation of the obtained results of direction solidification experiments under rotating magnetic field will be presented in this paper.Magnetic field of 0.5 T is created by rotating permanent magnet system driven by electric step motor.
基金the National Natural Science Foundation of China(11834012,51620105014,91963207,91963122 and 51902237)the National Key Research and Development Program of China(2018YFB0703603,2019YFA0704900 and SQ2018YFE010905)Foshan Xianhu Laboratory of Advanced Energy Science and Technology Guangdong Laboratory(XHT2020-004)。
文摘Synergistically regulating carrier and phonon transport on the nanoscale is extremely difficult for all thermoelectric(TE)materials without cage structures.Herein BaFe_(12)O_(19)/Bi_(2)Te_(2.5)Se_(0.5)thermoelectromagnetic nanocomposites are designed and synthesized as a benchmarking example to simultaneously tailor the transport properties on the nanoscale.A magneto-trapped carrier effect induced by BaFe_(12)O_(19)hard-magnetic nanoparticles(NPs)is discovered,which can lower the carrier concentration of n-type Bi_(2)Te_(2.5)Se_(0.5)matrix by 16%,and increase the Seebeck coefficient by 16%.Meanwhile,BaFe_(12)O_(19)NPs provide phonon scattering centers and reduce the thermal conductivity by 12%.As a result,the ZT value of the nanocomposites is enhanced by more than 25%in the range of 300-450 K,and the cooling temperature difference increases by 65%near room temperature.This work greatly broadens the commercial application potential of ntype Bi_(2)Te_(2.5)Se_(0.5),and demonstrates magneto-trapped carrier effect as a universal strategy to enhance the electro-thermal conversion performance of TE materials with high carrier concentration.
