Recently,Mg_(3)Sb_(2)-xBixalloys have attracted intensive attention,with the aim of maximizing the electrical transport performance via donor element doping,increasing the grain size,as well as electronic band structu...Recently,Mg_(3)Sb_(2)-xBixalloys have attracted intensive attention,with the aim of maximizing the electrical transport performance via donor element doping,increasing the grain size,as well as electronic band structure engineering.However,less attention has been paid to other significant factors,like how these intrinsic point defects and accompanied secondary phases influence thermoelectric properties.In this study,the microstructure and thermoelectric transport properties of Mg_(3.2)Sb_(0.5)Bi_(1.495-x)Te_(0.005)(x=0~0.2)compounds were systematically investigated,where tuning the Bi content shows the counter-intuitive impact on the thermoelectric properties.It was found that the Bipoor environment associated with Bi impurities facilitated the increment of cation vacancy formation energy and then increased the carrier concentration,leading to the enhancement of power factor.Simultaneously,the reduction of Bi-rich second phase content weakened the carrier scattering by grain boundaries whereas high carrier mobility was maintained.Moreover,the bipolar thermal conductivity decreased obviously due to the increased majority carrier concentration to suppress the intrinsic excitation.The synergistic optimization pushes the average ZT value(300-573 K)up to 0.95 in the Mg_(3.2)Sb_(0.5)Bi_(1.295)Te_(0.005)sample.Moreover,the calculated single-leg conversion efficiency is increased up to 9.7%with the hot-side temperature of 573 K,as the record-high value in this system.展开更多
It is very interesting to discover the elastic properties of engineering material palladium, especially its elastic anisotropy along Hugoniot states. We here investigate the evolution of its high pressure and temperat...It is very interesting to discover the elastic properties of engineering material palladium, especially its elastic anisotropy along Hugoniot states. We here investigate the evolution of its high pressure and temperature(PT) elastic ansotropy along Hugoniot using molecular dynamics simulations based on accurate classical interatomic potential. In order to testify the validity of the interatomic potential of Pd in describing the high PT elastic properties, we calculate its isothermal and adiabatic elastic moduli using molecular dynamics method. The obtained data are in good agreement with experimental data. From the isothermal elastic constants, we deduce the Hugoniot acoustic velocities and find that the resulting data are in good agreement with experimental acoustic velocity data. Based on the reliable elastic constants, we further investigate the spacial elastic ansotropy along Hugoniot PT states. It is found that the spacial elastic anisotropy of Pd increases along Hugoniot states.展开更多
Thermoelectric devices require thermoelectric materials with high figure-of-merit(ZT)values in the operating temperature range.In recent years,the Zintl phase compound,n-Mg_(3)Sb_(2),has received much attention owing ...Thermoelectric devices require thermoelectric materials with high figure-of-merit(ZT)values in the operating temperature range.In recent years,the Zintl phase compound,n-Mg_(3)Sb_(2),has received much attention owing to its rich chemistry and structural complexity.However,it hardly achieves high ZT values throughout the medium temperature range.Herein,by increasing the sintering temperature as much as possible,we successfully increased the average grain size of the compound by 15 times,and the grain boundary scattering was manipulated to obtain high carrier mobility of up to 180 cm^(2)V^(-1)s^(-1).Simultaneously,we optimized the Mg content for ultralow lattice thermal conductivity.We first doped the Mg_(3)Sb_(2)-based materials with boron for higher sintering temperature,good thermal stability,and higher hardness.The synergistic optimization of electrical and thermal transport resulted in excellent ZT values(0.62 at 300 K,1.81 at 773 K)and an average ZT of 1.4(from300 to 773 K),which are higher than the state-of-the-art values for n-type thermoelectric materials,demonstrating a high potential in device applications.展开更多
基金National Natural Science Foundation of China(Nos.52130106)Heilongjiang Touyan Innovation Team ProgramFundamental Research Funds for the Central Universities(FRFCU5710053021 and HIT.OCEF.2021014)。
文摘Recently,Mg_(3)Sb_(2)-xBixalloys have attracted intensive attention,with the aim of maximizing the electrical transport performance via donor element doping,increasing the grain size,as well as electronic band structure engineering.However,less attention has been paid to other significant factors,like how these intrinsic point defects and accompanied secondary phases influence thermoelectric properties.In this study,the microstructure and thermoelectric transport properties of Mg_(3.2)Sb_(0.5)Bi_(1.495-x)Te_(0.005)(x=0~0.2)compounds were systematically investigated,where tuning the Bi content shows the counter-intuitive impact on the thermoelectric properties.It was found that the Bipoor environment associated with Bi impurities facilitated the increment of cation vacancy formation energy and then increased the carrier concentration,leading to the enhancement of power factor.Simultaneously,the reduction of Bi-rich second phase content weakened the carrier scattering by grain boundaries whereas high carrier mobility was maintained.Moreover,the bipolar thermal conductivity decreased obviously due to the increased majority carrier concentration to suppress the intrinsic excitation.The synergistic optimization pushes the average ZT value(300-573 K)up to 0.95 in the Mg_(3.2)Sb_(0.5)Bi_(1.295)Te_(0.005)sample.Moreover,the calculated single-leg conversion efficiency is increased up to 9.7%with the hot-side temperature of 573 K,as the record-high value in this system.
基金Supported by the National Natural Science Foundation of China(41574076)the Basic Research of Technology Program of China under Grant No.JSHS2014404B002+1 种基金the Young Core Teacher Scheme of Henan Province under Grant No.2014GGJS-108key project of science and technology research of Henan Provincial Education Department under Grant No.18A140024
文摘It is very interesting to discover the elastic properties of engineering material palladium, especially its elastic anisotropy along Hugoniot states. We here investigate the evolution of its high pressure and temperature(PT) elastic ansotropy along Hugoniot using molecular dynamics simulations based on accurate classical interatomic potential. In order to testify the validity of the interatomic potential of Pd in describing the high PT elastic properties, we calculate its isothermal and adiabatic elastic moduli using molecular dynamics method. The obtained data are in good agreement with experimental data. From the isothermal elastic constants, we deduce the Hugoniot acoustic velocities and find that the resulting data are in good agreement with experimental acoustic velocity data. Based on the reliable elastic constants, we further investigate the spacial elastic ansotropy along Hugoniot PT states. It is found that the spacial elastic anisotropy of Pd increases along Hugoniot states.
基金supported by the National Natural Science Foundation of China(51771065 and 51871082)the Natural Science Foundation of Heilongjiang Province of China(ZD2020E003)。
文摘Thermoelectric devices require thermoelectric materials with high figure-of-merit(ZT)values in the operating temperature range.In recent years,the Zintl phase compound,n-Mg_(3)Sb_(2),has received much attention owing to its rich chemistry and structural complexity.However,it hardly achieves high ZT values throughout the medium temperature range.Herein,by increasing the sintering temperature as much as possible,we successfully increased the average grain size of the compound by 15 times,and the grain boundary scattering was manipulated to obtain high carrier mobility of up to 180 cm^(2)V^(-1)s^(-1).Simultaneously,we optimized the Mg content for ultralow lattice thermal conductivity.We first doped the Mg_(3)Sb_(2)-based materials with boron for higher sintering temperature,good thermal stability,and higher hardness.The synergistic optimization of electrical and thermal transport resulted in excellent ZT values(0.62 at 300 K,1.81 at 773 K)and an average ZT of 1.4(from300 to 773 K),which are higher than the state-of-the-art values for n-type thermoelectric materials,demonstrating a high potential in device applications.
