Q.Q. Wang

Simultaneous enhancement in thermoelectric power factor and phonon blocking in hierarchical nanostructured β-Zn4Sb3-Cu3SbSe4

In Pb and Te-free β-Zn4Sb3 based composites incorporated with nanophase Cu3SbSe4 (∼200 nm), we concurrently realize ∼30% increase in thermoelectric power factor (PF) through an energy filtering effect caused by carrier scattering at interface barriers, and around twofold reduction in lattice thermal conductivity due to interface scattering allowing the figure of merit (ZT) to reach 1.37 at 648 K in the composite system with 5 vol. % of Cu3SbSe4. Present results demonstrate that simultaneous enhancement of PF and phonon blocking can be achieved via proper design of a material-system and its microstructures, resulting in large increase in ZT of a material-system.

Resonant distortion of electronic density of states and enhancement of thermoelectric properties of β-Zn4Sb3 by Pr doping

The thermoelectric properties of Pr-doped compounds β-(Zn1−xPrx)4Sb3 (x = 0, 0.001, 0.002, 0.003) were investigated at the temperatures from 300 K to 615 K. The results indicate that Pr doping causes the resonant distortion of density of states of β-Zn4Sb3, as manifested by almost 2-fold increase of the density of state effective mass md* of β-Zn4Sb3, which results in ∼50 μV/K increase of the thermopower for the doped samples with x = 0.002 and 0.003. The thermal conductivity decreases substantially upon Pr doping. As a result, the figure of merit, ZT, of β-(Zn0.008Pr0.002)4Sb3 is ∼23% larger than that of the un-doped one and reaches 0.65 at 615 K, suggesting that Pr doping is an effective approach to raise ZT of β-Zn4Sb3.

Effects of Bi doping on the thermoelectric properties of β-Zn4Sb3

The thermoelectric properties of Bi-doped compounds (Zn1−xBix)4Sb3 (x=0,0.0025,0.005,0.01) were studied experimentally as well as theoretically. The results indicate that low-temperature (T<300 K) thermal conductivity of moderately doped (Zn0.9975Bi0.0025)4Sb3 reduces remarkably as compared with that of Zn4Sb3 due to enhanced phonon scattering of impurity (dopant). Electrical resistivity and Seebeck coefficient increase monotonically with increase in the Bi content resulting mainly from decrease in carrier concentration. Moreover, first-principle calculations were performed on the occupation options of Bi atoms in β-Zn4Sb3, which show that Bi will preferentially occupy the Zn sites and not Sb sites and act as donors, being consistent with the experimental observations. In addition, the lightly doped compound (Zn0.9975Bi0.0025)4Sb3 exhibits the best thermoelectric performance due to the improvement in both its thermal conductivity and Seebeck coefficient, whose figure of merit, ZT, is about 1.5 times large...

Synthesis, characterization and electrical properties of the new solid electrolyte materials Ce6−xErxMoO 15-δ (0.0 < x < 1.5)

A new series of oxides, Ce6-xErxMoO15-delta (0.0 less than or equal to x less than or equal to 1.5), was synthesized using wet-chemistry techniques. The precursors and resultant oxide powders were characterized by differential thermal analysis/thermogravimetry, x-ray diffraction, and IR, Raman and x-ray photoelectron spectroscopy. The formation temperature of the powders was found to be as low as 350degreesC. Ce6-xErxMoO15-delta crystallized to a fluorite-related cubic structure. The electrical conductivity of the samples was investigated by using ac impedance spectroscopy. This showed that the presence of Er was related to the oxygen-ion conductivity, and that the highest oxygen-ion conductivity was found in Ce6-xErxMoO15-delta (x = 0.4), ranging from 5.9 x 10(-5) S cm(-1) at 300degreesC to 1.26 x 10(-2) S cm(-1) at 700degreesC, respectively. This kind of material shows a potential application in intermediate-temperature solid oxide fuel cells.