Search

N-type thermoelectric materials PbTe doped with iodine (PbTe 1−x I x , x = 0.0001, 0.0003, 0.0007 and 0.001) were synthesized by high pressure and high temperature method (HPHT). Thermoelectric properties of PbTe 1−x I x are investigated in the range of 300–600 K. The carrier concentration of PbTe prepared by HPHT is more sensitive to I content compared to that of the PbTe 1−x I x sample prepared by other methods. The resistivities and the absolute values of Seebeck coefficients for PbTe 1−x I x increase while the thermal conductivities decrease with increasing temperature. A large power factor of 39.1 μW/(cmK 2 ) at room temperature is obtained with the carrier concentration of 9.7 × 10 18 cm −3 , which is much higher than that of Sb and Bi doped PbTe with the same synthesizing conditions. The high power factor is attributed to the high Hall mobility and large effective mass. The maximum figure-of-merit, ∼0.71 @ 600 K, is obtained for the samples with the carrier concentration of 9.7 × 10 18 cm −3 . [ABSTRACT FROM AUTHOR]

Polycrystalline BiCuSeO oxides are prepared by solid-state reaction followed by pressureless sintering (PLS) and high pressure sintering (HPS) methods. Both the experimental results and the density functional theory calculations indicate that the crystal defect concentrations of BiCuSeO can be reduced under the effect of high pressure. By comparing with the PLS sample, a larger power factor and a lower thermal conductivity can be obtained for the HPS sample. The maximum figure of merit ZT∼0.4 @ 800 K was obtained for the HPS sample, which is about 3 times higher than the PLS sample. These results indicate that the effect of high pressure is beneficial to modifying the microstructure and improving the thermoelectric performance of BiCuSeO oxyselenide. [ABSTRACT FROM AUTHOR]

In this paper, crack-free bulk thermoelectric material ZnSb was prepared rapidly by high pressure and high temperature (HPHT) method. Near a single-phase ZnSb specimen was obtained using nominal stoichiometric powder mixtures, which were indexed by powder X-ray diffraction. The temperature-dependent thermoelectric properties including the Seebeck coefficient and electrical resistivity were studied. The maximum power factor of ZnSb specimen prepared by HPHT reaches 10.8 μW/(cmK) at 637 K, which is comparable to the published data. The results show that the HPHT offers potential processing route to produce the thermoelectric material ZnSb quickly and effectively. [ABSTRACT FROM AUTHOR]

Thermoelectric material, Ag $_{1-}\textit{x}$ Pb $_{\textit{m}}$ SbTe $_{\textit{m}+2}$ ( x = 0·2, m = 10), have been successfully prepared by high pressure method. The pressure-dependent electrical transport and thermoelectric properties of Ag Pb SbTe were studied at room temperature. Electrical resistivity and Seebeck coefficient decreases with an increase of synthetic pressure. Thermal conductivities are nearly constant when the pressure is lower than 4 GPa. The carrier concentrations of Ag Pb SbTe were tuned by more than a factor of 100 through changing of synthetic pressure. These results indicate that high pressure technique provides a viable and controllable way of tuning the electrical transport properties for AgPb $_{\textit{m}}$ SbTe $_{\textit{m} + 2}$. [ABSTRACT FROM AUTHOR]

Recently, it was found that element semiconductor tellurium (Te) has a high thermoelectric performance. However, it needs to be doped with high-toxic arsenic (As) to tune the carrier concentration of Te. In this paper, low-toxic bismuth (Bi) was employed as dopant to optimize the thermoelectric performance of Te combining with a high-pressure synthesis method. The effect of substituting Bi on the electrical transport and thermal transport properties of Te has been investigated. The results show that the solubility limit of Bi in Te is about 0.1 mol%. However, the trace amounts of Bi doping can tune the carrier concentration of Te effectively and thereby optimize its power factor. The thermal conductivity of non-doped Te prepared by high pressure is much lower than that of the sample prepared at ambient pressure. And Bi doping can further decrease the value due to the phonons scattered by the heavy impurity atom. An enhanced figure of merit ZT ~ 0.72 was obtained at 517 K, which is about four times that of non-doped Te and is comparable to the state-of-the-art thermoelectric alloys with more complex composition such as BiTe and PbTe. [ABSTRACT FROM AUTHOR]

The structural properties of pyrochlore Eu2Zr2O7under high pressure have been studied by using Raman spectroscopy andin situangle-dispersive X-ray diffraction (ADXRD). The results of Raman spectra indicate that Eu2Zr2O7undergoes a reversible structural change around 21.2 GPa. The results of Rietveld refinements fromin situADXRD data indicate that the ordered pyrochlore structure (Fd-3m) transforms to the defect-cotunnite structure (Pnma) at 26.5 GPa. The phase transition is irreversible and the transformation process is mainly induced by the accumulations of anti-site defects of the cation sublattice and Frenkel defects on the anion sublattice. Besides, the bonds should play a more important role than the bonds in the process of the phase transformation. [ABSTRACT FROM AUTHOR]