Semiconductors are promising in photoelectric and thermoelectric devices, for which the thermal transport properties are of particular interest. However, they have not been fully understood, especially when crystallin...Semiconductors are promising in photoelectric and thermoelectric devices, for which the thermal transport properties are of particular interest. However, they have not been fully understood, especially when crystalline imperfections are present. Here, using cadmium telluride (CdTe) as an example, we illustrate how grain boundaries (GBs) affect the thermal transport properties of semiconductors. We develop a machine-learning force field from density functional theory calculations for predicting the lattice thermal conductivity (LTC) via equilibrium molecular dynamics simulations. The LTC of crystalline CdTe decreases with the relationship of κL~1/T in the simulation temperature range of 300 – 900 K, in which the isotropic LTC decreases from 3.34 to 0.23 W/ (m⋅K) due to the enhanced anharmonicity. More important, after introducing GBs, the LTC is suppressed in all directions, especially in the direction normal to the GB planes. More severe LTC suppression occurs in CdTe with Σ9 GB than that with Σ3 GB at 300 K, decreasing by 92.8% and 61.4% along the direction normal to the GB planes compared to the isotropic LTC of the crystalline CdTe, respectively. The decreased LTC is consistent with the weaker bonding near GB planes and lower shear modulus of the defective material. The analyses of the phonon dispersion curves, vibrational density of states, and phonon participation ratio indicate that the decreased LTC mainly arises from phonon scattering at GBs. Overall, our work highlights that GBs can greatly influence the LTC of semiconductors, thus providing a promising approach for thermal property design.展开更多
Magnesium aluminate spinel(MgAl2O4)is widely used in steel metallurgy industry.Thermal conductivity at high temperature signifcantly infuences the cooling process of blast furnace and the heat preservation of steel co...Magnesium aluminate spinel(MgAl2O4)is widely used in steel metallurgy industry.Thermal conductivity at high temperature signifcantly infuences the cooling process of blast furnace and the heat preservation of steel converter.The efect of external(temperature)and internal(antisite defect and grain boundary)factors on the thermal conductivity of MgAl2O4 was studied with non-equilibrium molecular dynamics.The main factors afecting the thermal conductivity of MgAl2O4 were summarized.In the temperature range of 100-2000 K,the results showed that the thermal conductivity of MgAl2O4 changed from 11.54 to 4.95 W/(m K)with the increase in temperature and was relatively stable at the temperature above 1000 K.The thermal conductivity of MgAl2O4 declined frst and then rose with the increase in the antisite defects,and the minimum value was 6.95 W/(m K)at the inversion parameter i=0.35.In addition,grain boundaries reduced the thermal conductivity of MgAl2O4 by 20%-30%at temperature below 1000 K comparing with the non-grain boundary system.The grain boundary rotation angle at temperature above 1000 K had less efect on the thermal conductivity than that below 1000 K.Present simulation scheme for thermal conductivity of MgAl2O4 can also be applied to the study of other nonmetallic ceramics.展开更多
文摘Semiconductors are promising in photoelectric and thermoelectric devices, for which the thermal transport properties are of particular interest. However, they have not been fully understood, especially when crystalline imperfections are present. Here, using cadmium telluride (CdTe) as an example, we illustrate how grain boundaries (GBs) affect the thermal transport properties of semiconductors. We develop a machine-learning force field from density functional theory calculations for predicting the lattice thermal conductivity (LTC) via equilibrium molecular dynamics simulations. The LTC of crystalline CdTe decreases with the relationship of κL~1/T in the simulation temperature range of 300 – 900 K, in which the isotropic LTC decreases from 3.34 to 0.23 W/ (m⋅K) due to the enhanced anharmonicity. More important, after introducing GBs, the LTC is suppressed in all directions, especially in the direction normal to the GB planes. More severe LTC suppression occurs in CdTe with Σ9 GB than that with Σ3 GB at 300 K, decreasing by 92.8% and 61.4% along the direction normal to the GB planes compared to the isotropic LTC of the crystalline CdTe, respectively. The decreased LTC is consistent with the weaker bonding near GB planes and lower shear modulus of the defective material. The analyses of the phonon dispersion curves, vibrational density of states, and phonon participation ratio indicate that the decreased LTC mainly arises from phonon scattering at GBs. Overall, our work highlights that GBs can greatly influence the LTC of semiconductors, thus providing a promising approach for thermal property design.
基金This work is sponsored by the National Natural Science Foundation of China(Grant Nos.21233010 and 51474047).
文摘Magnesium aluminate spinel(MgAl2O4)is widely used in steel metallurgy industry.Thermal conductivity at high temperature signifcantly infuences the cooling process of blast furnace and the heat preservation of steel converter.The efect of external(temperature)and internal(antisite defect and grain boundary)factors on the thermal conductivity of MgAl2O4 was studied with non-equilibrium molecular dynamics.The main factors afecting the thermal conductivity of MgAl2O4 were summarized.In the temperature range of 100-2000 K,the results showed that the thermal conductivity of MgAl2O4 changed from 11.54 to 4.95 W/(m K)with the increase in temperature and was relatively stable at the temperature above 1000 K.The thermal conductivity of MgAl2O4 declined frst and then rose with the increase in the antisite defects,and the minimum value was 6.95 W/(m K)at the inversion parameter i=0.35.In addition,grain boundaries reduced the thermal conductivity of MgAl2O4 by 20%-30%at temperature below 1000 K comparing with the non-grain boundary system.The grain boundary rotation angle at temperature above 1000 K had less efect on the thermal conductivity than that below 1000 K.Present simulation scheme for thermal conductivity of MgAl2O4 can also be applied to the study of other nonmetallic ceramics.
