The electronic structure and thermoelectric（TE） properties of PbS_xTe_（1-x）（x = 0.25, 0.5, and 0.75） solid solution have been studied by combining the first-principles calculations and semi-classical Boltzmann t...The electronic structure and thermoelectric（TE） properties of PbS_xTe_（1-x）（x = 0.25, 0.5, and 0.75） solid solution have been studied by combining the first-principles calculations and semi-classical Boltzmann theory. The special quasirandom structure（SQS） method is used to model the solid solutions of PbS_xTe_（1-x）, which can produce reasonable electronic structures with respect to experimental results. The maximum zT value can reach 1.67 for p-type PbS0.75Te0.25 and 1.30 for PbS0.5Te0.5 at 800 K, respectively. The performance of p-type PbS_xTe_（1-x） is superior to the n-type ones, mainly attributed to the higher effective mass of the carriers. The z T values for PbS_xTe_（1-x） solid solutions are higher than that of pure Pb Te and Pb S, in which the combination of low thermal conductivity and high power factor play important roles.展开更多
The electronic structure and thermoelectric（TE） properties of Mg2GexSn1-x（x = 0.25, 0.50, 0.75） solid solutions are investigated by first-principles calculations and semi-classical Boltzmann theory. The special qu...The electronic structure and thermoelectric（TE） properties of Mg2GexSn1-x（x = 0.25, 0.50, 0.75） solid solutions are investigated by first-principles calculations and semi-classical Boltzmann theory. The special quasi-random structure（SQS） is used to model the solid solutions, which can produce reasonable band gaps with respect to experimental results.The n-type solid solutions have an excellent thermoelectric performance with maximum zT values exceeding 2.0, where the combination of low lattice thermal conductivity and high power factor（PF） plays an important role. These values are higher than those of pure Mg2Sn and Mg2Ge. The p-type solid solutions are inferior to the n-type ones, mainly due to the much lower PF. The maximum zT value of 0.62 is predicted for p-type Mg2Ge（0.25）Sn（0.75） at 800K. The results suggest that the n-type Mg2GexSn1-x solid solutions are promising mid-temperature TE materials.展开更多
The layered 122 Zintl compounds have become an intriguing class of thermoelectric materials due to the promising electronic transport properties and inherently low thermal conductivity,showing the typical characterist...The layered 122 Zintl compounds have become an intriguing class of thermoelectric materials due to the promising electronic transport properties and inherently low thermal conductivity,showing the typical characteristics of"phonon-glass electron-crystal".Owing to the unprecedented performance tunability,the thermoelectric properties of the layered-structure compounds are completive with some traditional thermoelectric materials.Point defects involving vacancy,aliovalent doping and equivalent alloying atoms have been introduced to further enhance the thermoelectric properties.This review emphasizes the effects of various point defects on the thermoelectric parameters,and provides perspective on the strategies for increasing the thermoelectric figure of merit zT,which are believed to be applicable for improving the thermoelectric properties of many other compounds.展开更多
A nano-laminated Y_(3)Si_(2)C_(2) ceramic material was successfully synthesized via an in situ reaction between YH_(2)and SiC using spark plasma sintering technology.A MAX phase-like ternary layered structure of Y_(3)...A nano-laminated Y_(3)Si_(2)C_(2) ceramic material was successfully synthesized via an in situ reaction between YH_(2)and SiC using spark plasma sintering technology.A MAX phase-like ternary layered structure of Y_(3)Si_(2)C_(2) was observed at the atomic-scale by high resolution transmission electron microscopy.The lattice parameters calculated from both X-ray diffraction and selected area electron diffraction patterns are in good agreement with the reported theoretical results.The nano-laminated fracture of kink boundaries,delamination,and slipping were observed at the tip of the Vickers indents.The elastic modulus and Vickers hardness of Y_(3)Si_(2)C_(2) ceramics(with 5.5 wt%Y_(2)O_(3)) sintered at 1500℃were 156 and 6.4 GPa,respectively.The corresponding values of thermal and electrical conductivity were 13.7 W·m^(-1)·K^(-1) and 6.3×10^(5)S·m^(-1),respectively.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11647010 and 11704020)the Higher Education and High-quality and World-class Universities(Grant No.PY201611)the Fund for Disciplines Construction from Beijing University of Chemical Technology(Grant No.XK1702)
文摘The electronic structure and thermoelectric（TE） properties of PbS_xTe_（1-x）（x = 0.25, 0.5, and 0.75） solid solution have been studied by combining the first-principles calculations and semi-classical Boltzmann theory. The special quasirandom structure（SQS） method is used to model the solid solutions of PbS_xTe_（1-x）, which can produce reasonable electronic structures with respect to experimental results. The maximum zT value can reach 1.67 for p-type PbS0.75Te0.25 and 1.30 for PbS0.5Te0.5 at 800 K, respectively. The performance of p-type PbS_xTe_（1-x） is superior to the n-type ones, mainly attributed to the higher effective mass of the carriers. The z T values for PbS_xTe_（1-x） solid solutions are higher than that of pure Pb Te and Pb S, in which the combination of low thermal conductivity and high power factor play important roles.
基金supported by the National Natural Science Foundation of China(Grant No.11647010)the Foundation from the Higher Education and High-quality and World-class Universities(Grant No.PY201611)
文摘The electronic structure and thermoelectric（TE） properties of Mg2GexSn1-x（x = 0.25, 0.50, 0.75） solid solutions are investigated by first-principles calculations and semi-classical Boltzmann theory. The special quasi-random structure（SQS） is used to model the solid solutions, which can produce reasonable band gaps with respect to experimental results.The n-type solid solutions have an excellent thermoelectric performance with maximum zT values exceeding 2.0, where the combination of low lattice thermal conductivity and high power factor（PF） plays an important role. These values are higher than those of pure Mg2Sn and Mg2Ge. The p-type solid solutions are inferior to the n-type ones, mainly due to the much lower PF. The maximum zT value of 0.62 is predicted for p-type Mg2Ge（0.25）Sn（0.75） at 800K. The results suggest that the n-type Mg2GexSn1-x solid solutions are promising mid-temperature TE materials.
基金Supported by the National Key Research and Development Program of China(2018YFA0702100)the National Natural Science Foundation of China(21771123,51772186 and 51632005)the Program of Introducing Talents of Discipline to Universities(D16002)。
文摘The layered 122 Zintl compounds have become an intriguing class of thermoelectric materials due to the promising electronic transport properties and inherently low thermal conductivity,showing the typical characteristics of"phonon-glass electron-crystal".Owing to the unprecedented performance tunability,the thermoelectric properties of the layered-structure compounds are completive with some traditional thermoelectric materials.Point defects involving vacancy,aliovalent doping and equivalent alloying atoms have been introduced to further enhance the thermoelectric properties.This review emphasizes the effects of various point defects on the thermoelectric parameters,and provides perspective on the strategies for increasing the thermoelectric figure of merit zT,which are believed to be applicable for improving the thermoelectric properties of many other compounds.
基金the support from the Ningbo 3315 Innovative Teams Program,China(Grant No.2019A-14-C)This study was supported by the National Natural Science Foundation of China(Grant Nos.11975296 and 51811540402).
文摘A nano-laminated Y_(3)Si_(2)C_(2) ceramic material was successfully synthesized via an in situ reaction between YH_(2)and SiC using spark plasma sintering technology.A MAX phase-like ternary layered structure of Y_(3)Si_(2)C_(2) was observed at the atomic-scale by high resolution transmission electron microscopy.The lattice parameters calculated from both X-ray diffraction and selected area electron diffraction patterns are in good agreement with the reported theoretical results.The nano-laminated fracture of kink boundaries,delamination,and slipping were observed at the tip of the Vickers indents.The elastic modulus and Vickers hardness of Y_(3)Si_(2)C_(2) ceramics(with 5.5 wt%Y_(2)O_(3)) sintered at 1500℃were 156 and 6.4 GPa,respectively.The corresponding values of thermal and electrical conductivity were 13.7 W·m^(-1)·K^(-1) and 6.3×10^(5)S·m^(-1),respectively.
