Papers by Keyword: PbTe

Abstract: The mechanical properties of sintered nanostructured Pb_1-xCu_xTe (0 ≤ x ≤ 0.2) alloy systems were investigated using nanoindentation technique. The powder precursors of the designed systems were prepared by ball milling technique and sintered by hot isostatic pressing. Cu acts as a dopant in these alloy systems, and an increase in its concentration, up to x = 0.1, leads to a more dense and refined nanostructure along with enhancements in both hardness and Young’s modulus. The Cu addition caused an apparent embrittlement in the materials, and spalling of the materials was recognized when x exceeded 0.15. These results imply that design parameters of complex mechanical environments under thermal shocks and vibrations cannot be determined only in terms of hardness and Young’s modulus of thermoelectric systems like Pb_1-xCu_xTe alloys.

Abstract: We prepare Lead Telluride (PbTe) thin film by DC magnetron sputtering method. The powder precursors of Pb and Te purity 99.99 % ratio 1:1 were mixed. PbTe Powder was pressed using as sputtering target. DC magnetron sputtering condition, the base pressure is 3.2×10⁻³ Torr, applied the argon gas (purity 99.99%) in vacuum chamber to obtained working pressure at 50×10⁻³ Torr. The sputtering power is 25 W and sputtering time is 30 minutes. Phase identification, morphology and film thickness have been investigated by X−ray diffraction and scanning electron microscope. Electrical resistivity and Seebeck coefficient of the PbTe thin films have been investigated by four probe steady state method. The results demonstrated that the crystal phase of PbTe is face center cubic (FCC) structure. The average PbTe films yielded film thickness is around 460 nm, the average electrical resistivity is 17 Ω m and seebeck coefficient is 8.0×10⁻⁵ V K^─1.

Abstract: This study reports the cycle chemistries involved in depositing CdTe and PbTe nanofilms. An automated thin-layer flow cell electrodeposition system was used to deposit the films at room temperature. Cyclic voltammetry was used to study the Underpotential Deposition (UPD) of the compounds. The monolayer/cycle deposition rate was also monitored in order to insure that the film is depositing at a uniform rate. The chemical composition of the films was characterized using Energy-Dispersive X-ray Spectroscopy (EDS) on a Scanning Electron Microscope (SEM). The crystallinity of the films was studied using a glancing angle X-ray diffractometer. The bandgaps of the films were calculated using measured optical reflection data.

Abstract: The effects of nanophase additions on the thermoelectric properties of n-type AgPb18SbTe20 fabricated by combining fast melting and hot pressing were investigated. The presence of sovelthermally syntheszied AgPb18SbTe20 nanospheres or nanorods in the bulk yields remarkably improved thermoelectric properties. Nanophase additions produce a reduction in the Seebeck coefficent at about 300~550 K and the maximum Seebeck coefficient absolute values are, respectively, 378 and 380 μV·K-1 for LAST-18 with nanospheres and nanorods samples. The κ values of two samples with nanophases show a lower value in the entire temperature range compared to that of LAST-18 matrix. A maximum figure of merit, ZT=0.92 at 673K for the nanorod-containing composite is achieved mainly due to the reduced thermal conductivity. Furthermore, the temperature of ZT peak shift to a higher range originated from the enlarged energy gap.

Abstract: In this paper, we reported that lead telluride (PbTe) with continuous carrier concentration gradient, in which PbI2, Al and Zr were doped, were successfully fabricated by the unidirectional solidification method. The carrier concentration was optimized by adjusting the relation between the dopants and the carrier concentration gradient. The carrier concentration for the ingots was estimated from the resistance results which were measured by the one-probe method. The result shows that the carrier concentration was large at the initiation side and small at termination side of the solidified ingots. The degree of the carrier concentration gradient can be controlled by the holding time at a liquid state and the cooling rate from the liquid state. The carrier concentration gradient can be largely affected by the Al-dopant. The samples 0.07mol%PbI2-0.05mol%Zr-0.07mol%Al-PbTe, which were made from a liquid phase at 1200K held for 1h and cooled at 98K/h, showed a carrier concentration gradient ranging from 2×1024 to 1.5×1025 /m3. The effective maximum power for this continuous FGM is 20% larger than that of jointed FGM.