Yuanxu Wang

Thermoelectric properties of Heusler-type compound Fe2V1−xNbxAl

The transport properties are calculated within the full-potential linearized augmented plane-wave method and the semi-classical Boltzmann theory on the Heusler-type compound Fe2V1−xNbxAl. The obtained Seebeck coefficients are in reasonable agreement with experimental results. The majority carriers of stoichiometric Fe2VAl are holes. When V is slightly replaced by Nb, the Seebeck coefficient becomes negative rapidly resulting in the main carrier changing from hole to electron. σ/τ of stoichiometric Fe2VAl exhibits semiconductor behavior. However, it transits into semimetal when V is replaced by Nb at low temperature and all Nb-substituted samples exhibit semiconducting behavior above 100 K. The power factor S2σ/τ of stoichiometric Fe2VAl is relative small, and it increases greatly after Nb substitution below 360 K. The low temperature power factor of Fe2V1−xNbxAl (xu2009≠u20090) increases dramatically due to the enhanced Seebeck coefficient.

Electronic and optical properties of pure and Ce3+-doped MgS single crystals: A first-principles prediction

The electronic and optical properties for pure and Ce3+-doped MgS crystals have been investigated by using the first-principles total energy calculations. The results show that MgS:Ce has a direct band gap of 2.38 eV, and the top of the valence band is determined by S 3p and Ce 4f states and the bottom of the conduction band is determined by Mg 2p, 3s and Ce 4f, 5d states, respectively. The Ce–S bond shows more ionic character than the Mg–S bond. Our results suggest that the green emission from MgS:Ce is produced by doped cerium. Furthermore, it is shown that MgS:Ce is a promising dielectric material.

Thermoelectric properties of monolayer Sb2Te3

The successful demonstration of monolayer films as promising thermoelectric materials highlights alternative strategies to nanostructuring for achieving high thermoelectric efficiency. Due to this reason, the electronic structure and thermoelectric properties of the monolayer Sb2Te3 are studied by using the density functional theory and the semiclassical Boltzmann transport equation. The dynamical stability of the monolayer Sb2Te3 can be guaranteed by the absence of imaginary frequencies in the phonon band structure. The monolayer Sb2Te3 can reduce the lattice thermal conductivity. The Seebeck coefficient S of the p-type monolayer Sb2Te3 is almost three times as high as those of the n-type monolayer Sb2Te3. The power factor for p-type doping is significantly larger than that for the n-type doping. Our calculated ZT values for the monolayer Sb2Te3 are far higher than those of nanomaterials Sb2Te3, bulk Sb2Te3, and the eutectic PbTe-Sb2Te3 composites, indicating that the thermoelectric performance of low-dimensional structure is indeed superior.The successful demonstration of monolayer films as promising thermoelectric materials highlights alternative strategies to nanostructuring for achieving high thermoelectric efficiency. Due to this reason, the electronic structure and thermoelectric properties of the monolayer Sb2Te3 are studied by using the density functional theory and the semiclassical Boltzmann transport equation. The dynamical stability of the monolayer Sb2Te3 can be guaranteed by the absence of imaginary frequencies in the phonon band structure. The monolayer Sb2Te3 can reduce the lattice thermal conductivity. The Seebeck coefficient S of the p-type monolayer Sb2Te3 is almost three times as high as those of the n-type monolayer Sb2Te3. The power factor for p-type doping is significantly larger than that for the n-type doping. Our calculated ZT values for the monolayer Sb2Te3 are far higher than those of nanomaterials Sb2Te3, bulk Sb2Te3, and the eutectic PbTe-Sb2Te3 composites, indicating that the thermoelectric performance of low-di...