Papers by Keyword: Lead Telluride

Abstract: We present here a study on the electrical and structural properties of p-type PbTe films doped with CaF₂. The layers were grown by molecular beam epitaxy on freshly cleaved (111) BaF₂ substrates. The doping level was monitored by the CaF₂ solid source cell temperature (T_CaF2), which varied from 500 to 1150 °C. The films with low doping level, T_CaF2 ≤ 1010 °C, exhibited flat surfaces with crystalline quality close to the undoped PbTe sample. In contrast, samples with high levels of doping (T_CaF2 > 1010 °C) presented CaF₂ agglomerates on the surface and a worse crystal quality. The hole density at 77 K versus T_CaF2 oscillated between 1.3 × 10¹⁷ and 3.6 × 10¹⁷ cm^-3 and did not exhibit a systematic behavior as the fluoride supply is raised. The results indicate that CaF₂ is not an effective p-type dopant for PbTe, due to the abscence of a resonant level close to the valence band or to compensation of extrinsic dopant levels.

Abstract: In this article, the influence of structural and phase changes on the thermoelectric properties of PbTe doped with CdSe compounds of various molar concentrations were studied. The research showed that with a minimum value of the lattice parameter of the formed new phases in the PbTe matrix (at an impurity concentration of 0.5 mol%), the specific electrical conductivity and thermoEMF coefficient have a minimum value. A further increase in concentration leads to an increase in these parameters.

Abstract: We present the thermoelectric properties of individual PbTe (lead telluride) nanowire (NW) grown by a stress induced method. Temperature-dependent thermoelectric power and electrical conductivity in PbTe NW with diameter 125 nm were investigated in temperature ranging of 300−400 K. The PbTe NW was found to have a Seebeck coeficient S and electrical conductivity σ of −121 μV K⁻¹ and 138 S cm⁻¹ at 300 K, respectively. The calculated power factor (PF) of PbTe NW (d = 125 nm) demonstrate an enhancement, wich is higher than that have been previously reported in PbTe NWs. Such an enhanced thermoelectric performance can in part be attributed to the size effect of nanowires.

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: PbTe based semiconductors are characterized by a narrow energy gap and can be used for IR detectors, light emission diodes, lasers and thermoelectric devices. The objective of the present work was to study the effect of oxidation on the properties of n- and p-type PbTe samples prepared by powder metallurgy (bulk materials) and physical vapor deposition (thin films with thickness ∼1 μm). The samples were characterized by SEM, AES and XRD. The Hall effect and electrical conductivity of PbTe samples have been examined over the 80 – 300 K temperature range. The experimental results are accounted for in the framework of a model that is based on: 1- the fast diffusion of oxygen along grain boundaries (GB); 2 - oxygen absorption that generates acceptor states at GB (short time annealing) and the growth of PbTe oxides on GB with properties corresponding to wide band semiconductor (lengthy annealing); 3 - the creation of potential barriers on GB due to oxidation with a thermally activated dependence of the conductivity.

Abstract: AgxPbmSbTe2+m thermoelectric materials were fabricated using a combined process of mechanical alloying (MA) and spark plasma sintering (SPS). The compound powder was synthesized by mechanical alloying (MA) from elemental powders using a planetary mill after a short time, and high-density bulk samples were fabricated by spark plasma sintering (SPS) at low temperature within a short time (12 minutes). The P-type materials were obtained with electrical properties comparable to the newly reported data. The properties of P-type AgxPbmSbTe2+m-based materials could be improved by optimizing the composition and the process.

Abstract: The p-type (Bi0.2Sb0.8)2Te3/(Pb0.7Sn0.3)Te functional gradient material (FGM) was fabricated by hot-pressing the mechanically alloyed (Bi0.2Sb0.8)2Te3 and the 0.5 at% Na2Te-doped (Pb0.7Sn0.3)Te powders. Also, the n-type Bi2(Te0.9Se0.1)3/PbTe FGM was processed by hot-pressing the mechanically alloyed Bi2(Te0.9Se0.1)3 and the 0.3 wt% Bi-doped PbTe powders. With △T larger than 300°C, the p-type (Bi0.2Sb0.8)2Te3/(Pb0.7Sn0.3)Te FGM exhibited larger thermoelectric output power than those of the (Bi0.2Sb0.8)2Te3 and the 0.5 at% Na2Te-doped (Pb0.7Sn0.3)Te alloys. For the n-type Bi2(Te0.9Se0.1)3/PbTe FGM, the thermoelectric output power superior to those of the Bi2(Te0.9Se0.1)3 and the 0.3 wt% Bi-doped PbTe was predicted at △T larger than 300°C.