Te-doped Bi Research Articles

Modulation of the Internal Electric Field in Te-Doped Bi2MoO6 Nanosheets: Implication for the Photocatalytic Degradation of Rhodamine B and Photooxidation of Benzylamine

Modulation of the Internal Electric Field in Te-Doped Bi₂MoO₆ Nanosheets: Implication for the Photocatalytic Degradation of Rhodamine B and Photooxidation of Benzylamine

Revealing the Behavior of Interfacial Water in Te-Doped Bi via Operando Infrared Spectroscopy for Improving Electrochemical CO2 Reduction

Revealing the Behavior of Interfacial Water in Te-Doped Bi via Operando Infrared Spectroscopy for Improving Electrochemical CO₂ Reduction

Colloidal Synthesis of Te-Doped Bi Nanoparticles: Low-Temperature Charge Transport and Thermoelectric Properties.

Electronically doped nanoparticles formed by incorporation of impurities have been of great interest because of their controllable electrical properties. However, the development of a strategy for n-type or p-type doping on sub-10 nm-sized nanoparticles under the quantum confinement regime is very challenging using conventional processes, owing to the difficulty in synthesis. Herein, we report the colloidal chemical synthesis of sub-10 nm-sized tellurium (Te)-doped Bismuth (Bi) nanoparticles with precisely controlled Te content from 0 to 5% and systematically investigate their low-temperature charge transport and thermoelectric properties. Microstructural characterization of nanoparticles demonstrates that Te ions are successfully incorporated into Bi nanoparticles rather than remaining on the nanoparticle surfaces. Low-temperature Hall measurement results of the hot-pressed Te-doped Bi-nanostructured materials, with grain sizes ranging from 30 to 60 nm, show that the charge transport properties are governed by the doping content and the related impurity and nanoscale grain boundary scatterings. Furthermore, the low-temperature thermoelectric properties reveal that the electrical conductivity and Seebeck coefficient expectedly change with the Te content, whereas the thermal conductivity is significantly reduced by Te doping because of phonon scattering at the sites arising from impurities and nanoscale grain boundaries. Accordingly, the 1% Te-doped Bi sample exhibits a higher figure-of-merit ZT by ∼10% than that of the undoped sample. The synthetic strategy demonstrated in this study offers the possibility of electronic doping of various quantum-confined nanoparticles for diverse applications.

Microstructure and thermoelectric properties of p-type Bi 2Te 3–Sb 2Te 3 alloys produced by rapid solidification and spark plasma sintering

P-type Te-doped Bi 2Te 3–Sb 2Te 3 compounds were prepared using rapid solidification and spark plasma sintering (SPS) techniques. The microstructure and thermoelectric properties were evaluated as a function of the SPS temperature. The phase distribution was characterized by X-ray diffraction (XRD) and examined by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) area scanning. The thermoelectric properties were evaluated by a combination of thermal conductivity, electrical resistivity and Seebeck coefficient. The solidified powders consisted of homogeneous thermoelectric phase. As the SPS temperature increases, the microstructure become coarsen, resulting in the reduction of hardness. The thermoelectric figure of merit measured to be the maximum (3.05 × 10 −3/°C) at the SPS temperature of 430 °C.

Preferential orientation and thermoelectric properties of p-type Bi 0.4Sb 1.6Te 3 system alloys by mechanical alloying and equal channel angular extrusion

The p-type Bi 0.4Sb 1.6Te 3 system compounds with fine microstructure were prepared by mechanical alloying (MA) and equal channel angular extrusion (ECAE) in the present work. A preferentially orientated microstructure that the (1 1 0) plane preferentially orientated along the perpendicular direction to extrusion and the basal planes (0 0 l) preferentially orientated along the extrusion direction was formed in the ECAE process, and the orientation factors F of the basal planes (0 0 l) of the extruded alloys was about 0.36. The electrical and thermal transmission performances were strongly affected by the preferential orientation and the thermoelectric properties in the extrusion direction were obviously improved by the ECAE process. The maximum dimensionless figure of merit of the 4 wt.% Te-doped Bi 0.4Sb 1.6Te 3 alloys was obtained in the extrusion direction at testing temperature 343 K, ZT = 0.979.

Giant quantum oscillations of the longitudinal magnetothermopower at the electron topological transition induced by stretch of quantum wires of bismuth doped with Te

Thermoelectric and magneto-thermoelectric properties of quantum wires of bismuth doped with Te were investigated at electron topological transitions (ETT) induced by stretch in the temperature interval 4.2-300 K and magnetic fields up to 14T. Single Bi, Bi<Te> wires were obtained by the liquid phase casting by the Ulitovsky method. They were single crystals of strictly cylindrical form in a glass cover with orientation <1011> along the wire axis. In thin wires of Bi doped with Te a number of anomalies were found out at ETT, of the type of formation of new Fermi surface cavity (T-hole) induced by extension. The “giant” oscillations of the thermopower in magnetic field and singularities in deformation curves of thermopower and resistance may be referred to these anomalies. In general they give evidence that the intervally scattering of carriers plays the significant role in wires of Bi and Te-doped Bi in the low temperature range. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Determination of carrier density in Te-doped Bi nanowires

A promising approach is presented to characterize the carrier density in Te-doped Bi nanowires from their temperature-dependent resistance measurements, based on the comparison of the scattering rates due to charged impurity scattering and due to other scattering mechanisms that are independent of the carrier density. The result shows that the Te doping efficiency δe is only about 10%–15% for Te-doped Bi nanowires synthesized in an alumina template by molten-metal pressure injection. This analysis technique can be extended to other nanowire systems to provide valuable information regarding the carrier concentration and the Fermi energy for use in controlling and optimizing nanowire properties for specific applications.

Electronic transport in a 3-D network of 1-D Bi and Te-doped Bi quantum wires

The resistance ( R) and transverse magnetoresistance (TMR) of a high density network of 6 nm diameter wires of Bi and Bi doped with 0.14% Te in porous Vycor glass were measured. For pure Bi R increases as T decreases from 300 to 0.3 K . Below 5 K a sharp upturn in the resistance is observed; the order of magnitude of the resistance rise and the behavior of the MR are consistent with localization and electron–electron interaction theories of a one-dimensional disordered conductor in the presence of strong spin–orbit scattering. Addition of Te, which modifies the carrier density and scattering, reduces this resistivity increase, while the magnitude of the magnetoresistance is substantially enhanced.

Growth and electrical transport characteristics of Bi 2Sr 2Ca 1Cu 2O x and Bi 2Sr 2CuO x single-crystal whiskers using tellurium-doped precursors

Bi 2Sr 2CaCu 2O x (Bi2212) and Bi 2Sr 2CuO x (Bi2201) single-crystal whiskers were grown by annealing sintered Te-doped Bi–Sr–Ca–Cu–O precursors. The growth of Bi2212 or Bi2201 whiskers definitely depends on the Ca content of precursors; the optimal composition is Ca-rich Bi 2Sr 2Ca 2Cu 2Te 0.50O x for Bi2212 and Bi 2Sr 2CaCuTe 0.50O x for Bi2201. In the precursors Te ions exist in the phase of (SrCa) 3TeO 6. The whiskers contain no Te element. The Bi2212 whiskers have a critical temperature of about 80 K and the critical current with a multibranched structure of the current–voltage characteristics due to the intrinsic Josephson junctions along the c-axis is quite uniform, showing that the whiskers are homogeneous and of good quality. The Bi2201 whiskers show semiconducting resistance with no superconducting transition down to 4.2 K.

Growth and superconducting properties of Bi2Sr2CaCu2O8+δ single-crystal whiskers using tellurium-doped precursors

Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212) single-crystal whiskers were grown by annealing sintered Te-doped Bi–Sr–Ca–Cu–O precursors that had not passed through a melt-quenched glassy state, a process that is known well at this time. The optimum nominal composition of precursors is Ca-rich Bi2Sr2Ca2Cu2Te0.5Ox with a Te content of 0.5. The whiskers contain no Te element. The precursors are mainly composed of Bi2212 and (SrCa)3TeO6 (STO) phases. The STO or the element Te acts as a catalyst in enhancing whisker growth. The critical current (Ic) with a multibranched structure of the current–voltage characteristics due to the intrinsic Josephson junctions along the c axis is quite uniform, showing that the whiskers are homogeneous and of good quality.

Transport Properties of Bi-related Nanowire Systems

AbstractWe present here an electrical transport property study of Te-doped Bi nanowires, and Bi1−xSbx alloy nanowires embedded in a dielectric matrix. The crystal structure of the nanowires were characterized by X-ray diffraction measurements, indicating that the nanowires possess the same lattice structure as bulk Bi in the presence of a small amount of Te or Sb atoms. The resistance measurements of 40-nm Te-doped Bi nanowires were performed over a wide range of temperature (2 K≤ T ≤ 300 K), and the results are consistent with theoretical predictions. The 1D-to-3D localization transition and the boundary scattering effect are both observed in magneto-resistance measurements of Bi1−xSbx alloy nanowires at low temperatures (T &lt; 4 K).

Electronic transport properties of single-crystal bismuth nanowire arrays

We present here a detailed study of the electrical transport properties of single-crystal bismuth nanowire arrays embedded in a dielectric matrix. Measurements of the resistance of Bi nanowire arrays with different wire diameters (60\char21{}110 nm) have been carried out over a wide range of temperatures (2.0\char21{}300 K) and magnetic fields (0\char21{}5.4 T). The transport properties of a heavily Te-doped Bi nanowire array have also been studied. At low temperatures, we show that the wire boundary scattering is the dominant scattering process for carriers in the undoped single-crystal Bi nanowires, while boundary scattering is less important for a heavily Te-doped sample, consistent with general theoretical considerations. The temperature dependences of the zero-field resistivity and of the longitudinal magneto-coefficient of the Bi nanowires were also studied and were found to be sensitive to the wire diameter. The quantum confinement of carriers is believed to play an important role in determining the overall temperature dependence of the zero-field resistivity. Theoretical considerations of the quantum confinement effects on the electronic band structure and on the transport properties of Bi nanowires are discussed. Despite the evidence for localization effects and diffusive electron interactions at low temperatures $(Tl~4.0\mathrm{K}),$ localization effects are not the dominant mechanisms affecting the resistivity or the magnetoresistance in the temperature range of this study.

Fabrication and Transport Properties of Te-Doped Bi Nanowire Arrays

ABSTRACTTe-doped Bi nanowires with a 40 nm wire diameter have been successfully synthesized in anodic alumina templates by the pressure injection technique. Due to the unique semimetal-semiconductor transition that occurs in Bi nanowires, these systems exhibit a rather different temperature dependence in transport properties from their bulk counterparts. An improved theoretical model of this unique 1D nanowire system is developed based on the band structure of bulk bismuth. The temperature dependence of resistance for Bi nanowire arrays have been studied experimentally for various Te dopant concentrations and the results are compared with theoretical predictions.

Effect of extrusion temperature and dopant on thermoelectric properties for hot-extruded p-type Te-doped Bi 0.5Sb 1.5Te 3 and n-type SbI 3-doped Bi 2Te 2.85Se 0.15

The p-type Te-doped Bi 0.5Sb 1.5Te 3 and n-type SbI 3-doped Bi 2Te 2.85Se 0.15 compounds were fabricated by hot extrusion in the temperature range of 300–440°C under an extrusion ratio of 20:1. The grains of the two compounds contained many dislocations and were fine equiaxed (∼1.0 μm) owing to the dynamic recrystallization during the extrusion. The hot extrusion gave rise to a slightly preferred orientation of grains. The bending strength and the figure of merit of the two compounds increased with increasing the extrusion temperature. In addition, the Te and SbI 3 dopants significantly increased the figure of merit. The values of the figure of merit for the p-type 4.0 wt.% Te-doped Bi 0.5Sb 1.5Te 3 and n-type 0.05 wt.% SbI 3-doped Bi 2Te 2.85Se 0.15 compounds hot extruded at 440°C were 2.94×10 −3 and 3.05×10 −3 K, respectively.

Microstructure and Thermoelectric Properties of P-Type Bi 0.5Sb 0.5Te 0.5 Compounds Fabricated by Hot Pressing and Hot Extrusion

Bismuth telluride (Bi{sub 2}Te{sub 0.5}) compounds have been used as thermoelectric cooling and power conversion materials, since they have a high figure of merit at room temperature and can be fabricated easily and cost effectively. The crystal structure of Bi{sub 2}Te{sub 0.5} at room temperature is rhombohedral (a = 0.438 nm and c = 3.049 nm). This crystal structure is composed of atomic layers in the order of Te/Bi/Te/Te/Bi/Te/Bi/Te/Te/... along the c-axis. The Te/Te layers are considered to be weakly bound with van der Waals-like forces. The electrical and mechanical properties along the directions parallel to the cleavage planes are better than those along the c-axis. The distinct cleavage planes are perpendicular t the c-axis. Owing to the cleavage features, the crystal has poor mechanical properties and fabricating of miniature thermoelectric modules is difficult. Many attempts were made by sintering to fabricate miniature modules without cleavage. However, the sintering technique is not effective because the figure of merit of sintered compounds is lower than that of single crystals. In this work, the authors fabricated the p-type Te-doped Bi{sub 0.5}Sb{sub 0.5}Te{sub 0.5} compounds by both hot pressing and hot extrusion and then investigated the microstructure and thermoelectric properties of the compounds.

Magnetic Properties of Te-Doped Bi-Pb-Sr-Ca-Cu Superconductors

The magnetic properties of Te-doped Bi 1.4 Pb 0.6 Sr 2 Ca 2 Cu 3 Te x O y superconductors were studied. Samples with x= 0.05 to 0.2, fired at 850°C for 50 hours in air, showed zero resistance above 100K. The volume fraction of the superconducting phases was increased by Te doping, and was maximum at x=0.1. On measuring hysteresis loops at 77K, the residual magnetization for the sample with x= 0.1 was found to be much larger than that for x=0. The critical current density for Te-doped samples was improved under high magnetic fields. These results suggest that Te doping is effective for increasing the pinning force. WDX analysis indicated that high-Tc phases contained 0.6 at% Te.

Radio-Frequency Helicon Resonance in Tellurium-Doped Bismuth

Galvanomagnetic properties of Te-doped Bi are studied by means of helicon standing wave resonance in high magnetic field up to 65 kG at 4.2 K. Magnetoresistance derived from Q -value of the resonance increases linearly with magnetic field, which is the result of the inhomogeneous distribution of ionized Te atoms. The resonant frequency of helicon shows the large quantum oscillation, the amplitude of which is about 5% of the nonoscillatory part and is independent of the carrier concentration, but depends on the linear term of the magnetoresistance. The phase of the oscillation of the resonant frequency differs from that of the oscillation of the magnetoresistance. It is found that the oscillation of the resonant frequency arises mainly from the quantum carrier transfer between heavy mass band and light mass band. The origin of the phase difference is found to be the collision broadening of Landau level. It is further found that the oscillation of the resonant frequency is enhanced by the inhomogeneous dist...

The Nernst and the Seebeck effects in Te-doped Bi[sbnd]Sb alloys

AbstractThe Nernst and the Seebeck effects in Te-doped Bi95Sb5 and Bi88Sb12 alloy were investigated between 77°K and 300°K.N-type extrinsic behavior was observed for Te-doped (>1018cmȡ3) BiSb alloys in the measuring temperature range. Measurements of the Seebeck coefficient and the Magneto-Seebeck effect in these alloys yield the Fermi energy and the scattering mechanisms. Electron mobility deduced from measurements of the Nernst coefficient in these alloys, assuming acoustic mode lattice scattering, is found in good agreement with the results from the Hall effect and the magneto resistance measurements.

Effect of anisotropy on helicon dispersion relation in tellurium - doped bismuth

Abstract Microwave helicon transmission through Te-doped Bi was measured in a pulsed magnetic field. It was found that the dispersion relation depends strongly on the mass density. The effective mass as well as the carrier density were determined from the experiment.

On the mobility of electrons in bismuth doped with tellurium

A theoretical discussion of the electron mobility in Te-doped Bi is given. As a result its dependence on electron concentration and on temperature is found. When using Lax' energy-band model agreement is obtained with experiments.