Transport Properties Of Bi Research Articles

Effect of staggered sublattice potential on electronic and transport properties of Bi(111) pristine and hydrogen-passivated nanoribbons

We investigate the impact of staggered sublattice potential (SSP) on the electronic and transport properties of Bi(111) bilayer and nanoribbons through first-principle calculations and the nonequilibrium Green's function method. We find that the topological phase transition of Bi(111) bilayer from topologically nontrivial (Z 2 = 1) to topologically trivial (Z 2 = 0) occurs at Δ = 1.77 eV SSP. Our study also reveals that energy bandgap opens for both pristine zigzag and armchair nanoribbon as the strength of the SSP (Δ > 1.50 eV for armchair nanoribbons and Δ > 1.90 eV for zigzag nanoribbons) increases, transitioning from non-trivial metallic edge states to insulating edge states. Furthermore, we explore the influence of SSP on edge-passivated zigzag nanoribbon. Through edge passivation, the dangling bonds are eliminated. As a result, it requires 0.4 eV less SSP to open an energy gap in edge-passivated nanoribbons compared to pristine nanoribbons. These findings hold promise for the advancement of Bi(111) nanoribbon-based field-effect transistors and spintronic devices.

Impact of Ca(BO2)2 Doping on High-Tc Phase Formation and Transport Properties of Bi(Pb)-2223 Superconductor

Proper Doping of a high-temperature superconductor (HTS) Bi(Pb)-2223 is an effective route to prepare Bi(Pb)-2223 HTS with enhanced transport characteristics. In this paper, we studied the impact of Ca(BO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> doping on high-T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> phase formation kinetics and transport critical current density of Bi(Pb)-2223. Samples with a nominal composition of Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.7</sub> Pb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Ca <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2-x</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> [Ca(BO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ] <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> , x = 0 −0.15 were prepared by the solid-state reaction method. The phase evolution of the prepared materials was studied by X-ray diffraction analysis (XRD). The resistivity and critical current density were measured by the standard four-probe method. Scanning electron microscopy (SEM) combined with Energy Dispersive X-ray (EDX) microanalysis (SEM-EDX) was used to examine the microstructure and elemental composition of samples. The obtained results show that Ca(BO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> doping leads to the promotion of the high-T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> phase formation and enhancement of the transport critical current density ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_c)</i> in Bi(Pb)-2223 HTS.

Modulation of transport properties via S/Br substitution: solvothermal synthesis, crystal structure, and transport properties of Bi13S17Br3.

The solvothermal synthetic exploration of the Bi-S-halogen phase space resulted in the synthesis of two bismuth sulfohalides with common structural motifs. Bi13S18I2 was confirmed to have the previously reported composition and crystal structure. In contrast, the bromide analogue was shown to have a formula of neither Bi19S27Br3 nor Bi13S18Br2, in contrast to the previous reports. The composition, refined from single crystal X-ray diffraction and confirmed by elemental analysis, high-resolution powder X-ray diffraction, and total scattering, is close to Bi13S17Br3 due to the partial S/Br substitution in the framework. Bi13S18I2 and Bi13S17Br3 are n-type semiconductors with similar optical bandgaps of ∼0.9 eV but different charge and heat transport properties. Due to the framework S/Br disorder, Bi13S17Br3 exhibits lower thermal and electrical conductivities than the iodine-containing analogue. The high Seebeck coefficients and ultralow thermal conductivities indicate that the reported bismuth sulfohalides are promising platforms to develop novel thermoelectric materials.

Impact of Boron Nitride Additive on the Phase Formation and Transport Properties of Bi(Pb)-2223 Superconductor

Doping of a high-temperature Bi(Pb)-2223 superconductor with various additives, which can act as pinning centers and / or accelerate the formation of a superconducting phase, is an effective tool for obtaining Bi(Pb)-2223 samples with improved characteristics. In this paper, we studied the effect of the addition of hexagonal boron nitride (h-BN) on the phase formation and critical transport current density of ceramic samples Bi(Pb)-2223. Samples with a nominal composition of Bi1.7Pb0.3Sr2Ca2Cu3Oy [BN]x, x = 0–0.25 were prepared by the solid-phase reaction method. Two different doping methods were used: the introduction of hand-ground BN powder at the initial stage of synthesis and the addition of BN powder subjected to high-energy grinding in a ball mill before pelletizing. The phase composition of the obtained samples was studied by X-ray diffraction. The microstructure and elemental composition of the samples were studied using a scanning electron microscope with an X-ray microanalyzer. The resistivity and critical current density were measured using the standard four-probe method. The results show that boron nitride is a suitable additive to increase the rate of formation and critical transport current density Bi(Pb)-2223.

Some effects of the doping with alpha - Al_2O_3 nanoparticles in the transport properties of Bi_1.65 Pb_0.35 Sr_2Ca_2 Cu_3O_y ceramic superconductors

We present a preliminary study on the effects of alpha - Al_2O_3 nanoparticles (NPs) in the transport properties of Bi_1.65 Pb_0.35 Sr_2Ca_2 Cu_3O_y ((Bi,Pb)-2223) ceramic samples. The (Bi,Pb)-2223 samples were synthesized by the solid state reaction method and alpha - Al_2O_3 NPs, with concentrations ranging from 0.1 to 0.8 wt. percent (% wt.), were added before the last heat treatment. All samples were characterized by means of X-rays diraction patterns, and temperature and magnetic eld dependence of the electrical resistivity, rho(T;Ba). From the experimental (T;Ba) data we extracted the critical temperature dependence of the % wt. of alpha - Al_2O_3 NPs, and by using the Arrheniusplot the eective pinning energy has been also determined. The results indicate that mostly of the transport properties are optimized for the sample B03.

Magnetic and Transport Properties of Bi0.5−x Pr x Ca0.5MnO3(0.0 ≤ x ≤ 0.50) Manganites

In this work, the effect of Pr doping at the Bi site on the critical behavior and magnetocaloric and transport properties of Bi0.5−x Pr x Ca0.5MnO3 (0.0 ≤ x ≤ 0.50) manganite synthesized by sol–gel method is reported. An increase in Curie temperature (T C) with an increase in Pr content is observed. The samples with x = 0.0–0.40 show first-order phase transition whereas the sample with x = 0.50 shows second-order phase transition near T C. The estimated values of critical exponents β = 0.75 and γ = 0.82 for the sample with x = 0.50 do not fall into any universality class. The sample with x = 0.50 shows maximum magnetic entropy change (|ΔS m| = (1.22 J kg−1 K−1) at T C in an applied magnetic field of 40 kOe, which is associated with magnetocaloric effect (MCE). All the samples show semiconducting behavior and also follow Mott’s variable range hopping (VRH) model below the charge ordering temperature (T CO). The changes in magnetic and transport properties are correlated with the changes in the structural parameters of the samples. The results are discussed in view of the effect of Pr doping on the 6s2 lone pair character of Bi3+ ions and disorder in the samples.

Thermoelectric transport properties of Bi–Te based thin films on strained polyimide substrates

Effect of stress on lattice defect concentration and thermoelectric properties of Bi–Te based thin films is investigated. Both Bi–Sb–Te and Bi–Se–Te films were individually sputtered on a stretched polyimide (PI) substrate and annealed at elevated temperature. With the PI strain varying from 0% to 10%, the carrier concentration increases triple times for the Bi–Sb–Te films and decreases by 35% for the Bi–Se–Te films. The Seebeck coefficient and electrical resistivity are also found to vary monotonically with PI strain. A stress-mediated Te vacancy formation mechanism is proposed to explain the changes of thermoelectric properties of Bi–Te films on strained PI substrates.

Influence of porosity on the transport properties of Bi2Te3-based alloys by field-assisted sintering

Abstract

Magnetic and charge ordering properties of Bi0.2Ca0.8Mn0.9X0.1O3 (where X = Ti, Cr, Fe, Co, Ni, Cu)

Structural, magnetic and transport properties of Bi0.2Ca0.8Mn0.9X0.1O3 (where X = Ti, Cr, Fe, Co, Ni, Cu) have been investigated. The parent sample Bi0.2Ca0.8MnO3 (BCMO) exhibits robust charge-ordered antiferrromagnetic (COAFM) phase with charge ordering temperature (TCO) ∼155 K and AFM Neel temperature (TN) ∼105 K. TCO decreases by ∼10 K and ∼33 K, respectively, in Ni2+ and Cu2+ doped samples, while it increases by 42 K in Ti4+ doped sample. In case of Fe3+, Co3+ and Cr3+ doped samples charge-ordering (CO) completely melts. The paramagnetic (PM) to ferromagnetic (FM) transition temperatures (TC) of doped samples have lower values as compared to undoped one. In addition, a spin glass (SG) state is observed in all the samples and the magnetic state at T < TC is akin to a cluster glass (CG) for undoped and Ni, Cu, Ti doped samples formed due to the presence of FM clusters in COAFM matrix. Furthermore, the enhancement in resistivity in all the doped samples with respect to undoped one has been observed. Based on the present study it has been proposed that the disorder induced by doping on the Mn site and magnetic exchange interactions between Mn and doped ions play a key role in explaining magnetic and electrical properties.

Magnetic and transport properties of phase-separated manganite [formula omitted

Abstract We have investigated the magnetic and transport properties of Bi 0.1 La 0.5 Ca 0.4 MnO 3 manganite, systematically. Four distinct feature temperature points in the temperature dependence of the magnetization curve M ( T ) occurring at ∼ 218 K , ∼ 181 K , ∼ 112 K and ∼ 38 K are observed; these are suggested to be related to charge ordered (CO), weak ferromagnetic (FM), strong FM, and blocked metastable state. These temperature points can be changed by applying magnetic fields. The field-cooled (FC) M ( T ) curves show an obvious thermal hysteresis between the FC cooling (FCC) and FC warming (FCW) measuring process. The large variation between the FC and zero-field-cooled (ZFC) magnetization curves at low temperatures reflects the existence of blocked metastable states separated by high energy barriers. The blocked state can be weakened or eventually destroyed by applying magnetic fields. The field dependence of the magnetization and resistivity at both 5 K and 130 K shows that the magnetic and electrical transport properties are tightly correlated with the same critical field. The results indicate that CO and FM phases coexist in the sample at low temperatures. The local lattice distortion induced by the Bi 3+ doping may play an important role in the complex magnetic and transport properties of the sample.

Synthesis, X-ray diffraction analysis, and transport properties of Bi5−xLnxNbO10(Ln = La, Gd, and Y) oxide-ion conductors

The effects of partial substitutions of Bi by La, Gd, and Y on the structure, thermal expansion and transport properties of modulated fluorite-type Bi5NbO10 were investigated using X-ray thermodiffraction, alternative current impedance spectroscopy and the Wagner polarization method. Through conventional solid-state syntheses, the solid solutions Bi5−xLnxNbO10 exist up to about x ∼ 0.25 for La, and to x ∼ 0.5 for Gd and Y. A doubling of their thermal expansion coefficient is observed above 540 °C. The type-II incommensurate modulation of these phases is correlated to the nature and amount of substitute, and disappears above 800 °C. Except for Bi5NbO10, which appears to be a pure ionic conductor, most of the solid solutions exhibit mixed conductivity with predominant ionic transport. Partial Gd and Y substitutions favor electron conductivity in the low temperature range, probably due to bismuth partial oxidation.

Inhomogeneous distribution of uniaxial compacting pressure and its effects on transport properties of Bi 1.65Pb 0.35Sr 2Ca 2Cu 3O y superconductors

Abstract We have measured the temperature dependence of the electrical resistivity ρ ( T , B a ) in polycrystalline Bi 1.65 Pb 0.35 Sr 2 Ca 2 Cu 3 O y superconductors under two conditions: B a =0 and B a =43 mT, where B a is the applied magnetic field. Powders of this material were uniaxially pressed at 217 MPa and thermally treated to obtain cylindrical samples with similar dimensions. The physical properties of the two interfaces of these samples were investigated: the first, where the piston used in the compacting process has a direct mechanical contact with the powders, referred to as A, and the other one, which is parallel to the former, referred to as B. We have found appreciable differences in the degree of texture between these faces from X-ray diffractometry. For transport measurements, two specimens with slab form were cut from the same sample. The first was extracted from the face A and the second one was cut along the thickness of the samples, from the face A to B. The temperature dependence of the electrical resistivity at zero applied magnetic field shows similar values of the critical temperatures in both samples, but appreciable difference in the offset temperatures was observed when a magnetic field of 43 mT is applied. These features are discussed assuming an inhomogeneous distribution of uniaxial compacting pressure in these ceramic samples.

Thermal stability and hopping conduction in Bi4Sr3Ca3CuxOy glasses (x = 4–9)

Abstract The thermal stability and transport properties of Bi 4 Sr 3 Ca 3 Cu x O y glasses with different Cu contents, 4 ≤ x ≤ 9, and Cu valence states, R(Cu + ) = Cu + /(Cu + + Cu 2+ ) with 0.7 ≤ R ≤ 1, have been examined. The Cu content dependence of thermal stability, electrical conductivity and activation energy for conduction is not monotonic, but the magnitudes of these properties change at the composition x ≅ 6.5. The effect of R (Cu + ) on the conduction of BiSrCaCuO glasses has been measured and the conductivity is analyzed using the Mott equation for electron conduction of glasses containing transition metal ions; the results suggest that the polaron hopping mechanism between Cu + and Cu 2+ is appropriate for the conduction of all Bi 4 Sr 3 Ca 3 Cu x O y glasses irrespective of Cu content. A new structure model, particularly on the role of Cu + , has been proposed for the present glasses, in which Cu + ions act as both network formers and modifiers depending on the ratio of Cu + Bi 3+ .

Electrical transport properties of Bi3Ni under helium irradiation and hydrogen implantation

The authors present data on the effects of alpha irradiation and H implantation on the electrical resistivity, rho , and the superconducting Tc of Bi3Ni. Two regimes of flux can be distinguished. At low doses, a large resistivity increase is due to atomic disorder irrespective of the impinging ion ( alpha or H); at the same time, only a slight Tc decrease is measured, in contrast with what is observed in A15 compounds. At high doses, specific effects due to H implantation are seen, probably implying significant modification of the electronic structure. There are indications that H enters the lattice as an interstitial, but that it also forms microbubbles.