Bismuth Diffusion Research Articles

Diffusion behavior of bismuth in eco-friendly Bi–S based free cutting steel at high temperature

Deformation cracks during continuous casting and hot rolling are easy to occur in the Bi–S based free cutting steel, and the cracks are related to the diffusion of bismuth. The diffusion behavior of bismuth in the steel and the effect of the microstructure and alloying elements were studied by the diffusion annealing experiment combined with SEM, EDS and TEM analysis. The results show that the bismuth tends to diffuse along the grain boundaries (GBs) and the interfaces between the MnS phase and steel matrix, and then enrich to form the bismuth phases. The bismuth phases with lower melting point would be in liquid form at high temperature and resulted in the cracks along the GBs and interfaces. The bismuth diffusion is more likely to occur toward the parallel rolling direction than the vertical rolling direction in the steel because of the pearlite and MnS phases with the long strip shape and banded distribution. The addition of boron and titanium has the effect of inhibiting the diffusion of bismuth in the steel, which is mainly attributed to the faster diffusion rate of boron and the priority to occupy the defect sites of the GBs and the interfaces between the MnS phase and steel matrix.

Atomistic view onto solid state dewetting: Thin bismuth films with and without strain gradient

We present a detailed study of solid state dewetting choosing epitaxial bismuth films on silicon as a model system. Exploiting both diffraction and imaging methods, we determine atomistic parameters like unit cell coverage, lattice spacings and gradients thereof through the analysis of x-ray diffraction crystal truncation rods. A different dewetting behavior of samples with and without strain gradient is revealed. Additionally, we discuss possible reasons for the impeding influence of a strain gradient, such as a reduced interface energy or increased step edge diffusion energy barrier, which we quantify by using a Johnson-Mehl-Avrami-Kolmogorov model. A model for the step edge self diffusion of Bismuth is presented.

The Process of Dispersing Bismuth Atoms into Iridium via an Intermediate Monolayer of Graphite

It is first revealed by thermodesorption spectroscopy that when bismuth atoms diffuse the indium atoms through an intermediate graphite layer, they show certain characteristic features. In the Ir (111)-C system at 1400 K δ = 0.4 ± 0.05 and diffusion δBi = Ndif/N = 2.5 × 10-3 bismuth atoms in the Ir(111)-C system. The amount of intercalated and diffused bismuth depends on the electrical field, i.e., on the positive potential in the Ir(111)-C system. It has been noted that a considerable diffusion of bismuth into iridium started at 180 V and increased up to 3000 V. The activation energies for bismuth diffusion into and from iridium were calculated to be En1 = 6.05 ± 0.05 eV and E1n = 6.3 ± 0.1 eV, respectively.

Interaction study between MOX fuel and eutectic lead–bismuth coolant

In the frame of the MYRRHA reactor project, the interaction between fuel pellets and the reactor coolant is essential for safety evaluations, e.g. in case of a pin breach. Therefore, interaction tests between uranium–plutonium mixed oxide (MOX) pellets and molten lead bismuth eutectic (LBE) have been performed and three parameters were studied, namely the interaction temperature (500 °C and 800 °C), the oxygen content in LBE and the stoichiometry of the MOX (U0.7Pu0.3O2−x and U0.7Pu0.3O2.00). After 50 h of interaction in closed containers, the pellet integrity was preserved in all cases. Whatever the conditions, neither interaction compounds (crystalline or amorphous) nor lead and bismuth diffusion into the surface regions of the MOX pellets has been detected. In most of the conditions, actinide releases into LBE were very limited (in the range of 0.01–0.15 mg), with a homogeneous release of the different actinides present in the MOX. Detected values were significantly higher in the 800 °C and low LBE oxygen content tests for both U0.7Pu0.3O2−x and U0.7Pu0.3O2.00, with 1–2 mg of actinide released in these conditions.

Molecular beam epitaxy and properties of GaAsBi/GaAs quantum wells grown by molecular beam epitaxy: effect of thermal annealing

We have grown GaAsBi quantum wells by molecular beam epitaxy. We have studied the properties of a 7% Bi GaAsBi quantum well and their variation with thermal annealing. High-resolution X-ray diffraction, secondary ion mass spectrometry, and transmission electron microscopy have been employed to get some insight into its structural properties. Stationary and time-resolved photoluminescence shows that the quantum well emission, peaking at 1.23 μm at room temperature, can be improved by a rapid annealing at 650°C, while the use of a higher annealing temperature leads to emission degradation and blue-shifting due to the activation of non-radiative centers and bismuth diffusion from the quantum well.

Microstructure development of BiFeO3–PbTiO3 films deposited by pulsed laser deposition on platinum substrates

BiFeO3–PbTiO3 films around the morphotropic phase boundary were deposited by pulsed laser deposition on polycrystalline Pt/TiOx/SiO2/Si substrates. X-ray analysis confirms that 0.6BiFeO3–0.4PbTiO3 films are (001) tetragonal preferentially orientated due to lattice matching with the underlying substrate. The misfit strain at the substrate–film interface is relieved by a ∼19% orientation transformation from (001) to (100) due to the lattice mismatch at the substrate–film interface and the difference in thermal expansion coefficients of the substrate and deposited film. 0.7BiFeO3–0.3PbTiO3 films are mixed-phase rhombohedral-tetragonal with (001)/(111) preferential orientation due to the lattice match to the (111) and (100) of the underlying platinum as well as to being close to the morphotropic phase boundary. Inconsistent structural and electrical properties in reported BiFeO3–PbTiO3 films are explained in terms of film morphology and diffusion of bismuth into platinum. Films below ∼220nm thickness produce short circuits due to a Volmer–Weber growth mechanism which results in physical defects within the films. Films above this critical thickness also produce variable electrical properties due to diffusion of bismuth into the underlying platinum electrode which has been confirmed by energy dispersive X-ray spectroscopy.

Revealing Bismuth Oxide Hollow Nanoparticle Formation by the Kirkendall Effect

We study the formation of bismuth oxide hollow nanoparticles by the Kirkendall effect using liquid cell transmission electron microscopy (TEM). Rich dynamics of bismuth diffusion through the bismuth oxide shell have been captured in situ. The diffusion coefficient of bismuth through bismuth oxide shell is 3-4 orders of magnitude higher than that of bulk. Observation reveals that defects, temperature, sizes of the particles, and so forth can affect the diffusion of reactive species and modify the kinetics of the hollowing process.

The p-type doping of vacuum deposited ZnTe thin films with bismuth by a new technique of using nano-spheres

The present paper reports the successful doping of vacuum evaporated zinc telluride (ZnTe) thin films with bismuth by a new technique of using nano-spheres. The discontinuous films of bismuth (the dopant material), containing bismuth in the form of nano-spheres, were prepared by vacuum evaporation and the ZnTe films were then deposited on top of them. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were used to ascertain the formation of discontinuous bismuth films and the proper diffusion of bismuth in ZnTe films, respectively. After doping, the carrier concentration of the ZnTe films was found to increase by an order of the magnitude. The electrical conductivity also improved significantly. The photoconductivity and photo-response properties of the doped films were also analysed.

Real-Time In Situ Atomic Force Microscopy Imaging of Bismuth Crystal Growth

We have performed real-time atomic force microscopy (AFM) imaging of bismuth crystals that were grown under electrochemical control at low overpotentials to ensure a slow growth rate and allow in situ observation of the growth. A two step chronoamperometric potential was applied to a boron-doped diamond (BDD) working electrode with a short high overpotential, -0.4 V (2 s), to nucleate the bismuth, and then a long low overpotential for slow growth, -0.32 V (4.4 h). Growth rates of individual crystals and detailed growth mechanisms could be followed in real time because of the slow crystal growth. The close proximity of the AFM tip and tip holder to the working electrode appears to hinder the diffusion of bismuth to the BDD surface, as evidenced by the significantly lower density of crystals under the cantilever as compared to the rest of the electrode, therefore slowing down the growth process.

Effect of Ta Nanobarrier in Magnetron Sputtering of Nd-Doped SrBi2Ta2O9 Thin Films

SrBi2Ta2O9 (SBT) is a bismuth layered perovskite with attractive ferroelectric properties for random access memory applications. Our previous studies showed that Nd-doped SBT (SNBT) thin films exhibited an improved remnant polarization and reduced coercivity. This paper concentrates on the effect of Ta nanobarrier in between the SNBT and the Pt layers. Without the nanobarrier, severe bismuth diffusion is revealed by the secondary ion mass spectroscopy. However, with a nano layer (up to 2 nm) of Ta metal, the interfacial diffusion is effectively suppressed even at 800 degrees C. Details of the composition profiling, film crystallinity and remnant polarization are discussed in view of the nanobarrier thickness.

The influence of annealing at different temperatures and atmospheres on the optical rotation of Bi12SiO20 crystals

Abstract The optical activity changes in Bi 12 SiO 20 (BSO) crystals induced by thermal annealing treatments are studied. It is found that the annealing in vacuum and hydrogen atmosphere causes decreasing of the optical rotation. Thermal treatment annealing induces reduction of Bi-ions to metallic bismuth on the surface as well as oxygen and bismuth diffusion and evaporation is supposed. Annealing in oxygen leads to partial recovery of the oxygen content in the crystals and the optical activity values tends to approach the level of un-annealed BSO crystal.

Low temperature processing and chacterization of SrBi2Nb2o9 thin films grown by pulsed laser ablation

Ex-situ grown thin films of SrBi2Nb2O9 (SBN) were deposited on platinum substrates using laser ablation technique. A low substrate-temperature-processing route was chosen to avoid any diffusion of bismuth into the Pt electrode. It was observed that the as grown films showed an oriented growth along the ′c′-axis (with zero spontaneous polarization). The as grown films were subsequently annealed to enhance crystallization. Upon annealing, these films transformed into a polycrystalline structure, and exhibited excellent ferroelectric properties. The switching was made to be possible by lowering the thickness without losing the electrically insulating behavior of the films. The hysteresis results showed an excellent square-shaped loop with results (Pr = 4 uC/cm2; Ec = 90 kV/cm) in good agreement with the earlier reports. The films also exhibited a dielectric constant of 190 and a dissipation factor of 0.02, which showed dispersion at low frequencies. The frequency dispersion was found to obey Jonscher's universal power law relation, and was attributed to the ionic charge hopping process according to earlier reports. The dc transport studies indicated an ohmic behavior in the low voltage region, while higher voltages induced a bulk space charge and resulted in non-linear current-voltage dependence.

A novel fabrication method for stoichiometric strontium bismuth tantalate thin films for memory devices

A novel method of processing ferroelectric thin films to eliminate excess bismuth is reported. Rapid thermal annealing initiates the crystallization of bismuth layer- structured ferroelectric thin films. Subsequent crystallization annealing for longer periods improves the crystallinity of the thin films. During annealing bismuth is known to diffuse to the surface and into the electrode, which is deleterious to the device performance. Forming-gas annealing after the rapid thermal annealing (prior to the crystallization annealing) reduces the bismuth diffusion into the electrode significantly. The suppression of bismuth diffusion into the electrode and the elimination of excess bismuth in the films improves and stabilizes the electrical properties of the capacitors, in particular their electronic conduction.

Volume expansion during reaction sintering of γ-Bi 12SiO 20

Preparation of γ-Bi 12SiO 20 from a compacted mixture of α-Bi 2O 3 and SiO 2 powders is described. A very large volume expansion, related to the phase formation, is observed during heat treatment at 600°C. It is shown that the dedensification results from a preferential diffusion of bismuth and oxygen ions towards SiO 2, through the layer of γ-Bi 12SiO 20 which forms around a silica grain. The expansion begins when γ-Bi 12SiO 20 grains form a continuous skeleton. When bismuth oxide grains are isolated in the skeleton, expansion and reaction rates are proportional. A quantitative model is proposed to describe this situation assuming an isotropic matter transfer and no coalescence between the γ-Bi 12SiO 20 grains.

Recoil Spectrometry and RBS studies of strontium bismuth tantalate films on Pt/Ti electrodes

Abstract Heavy Ion Elastic Recoil Detection Spectrometry and Rutherford Backscattering Analysis have been used to analyse thin films of strontium bismuth tantalate (SBT). This study uses these analysis techniques to investigate the interdiffusion of various elements in SBT/Pt/Ti/SiO2/Si structures which occurs during the annealing process. Evidence of diffusion of bismuth through the platinum electrode and titanium is shown within the platinum electrode.

Characteristics of spin-on ferroelectric SrBi2Ta2O9 thin film capacitors for ferroelectric random access memory applications

We report on the properties and characterization of SrBi2Ta2O9 (SBT, or Y − 1) thin film capacitors for ferroelectric random access memory (FERAM) applications. The films were prepared by spin-coating from carboxylate precursors. The remanent polarization (Pr) was 5−6 μC/cm2 and the coercive field was ∼55 kV/cm. Excellent fatigue endurance was observed up to 1011 cycles. Auger analysis indicates bismuth diffusion through the Pt electrode after capacitor anneal which might require excess Bi in the precursor solution for stoichiometry control. No detectable amount of α emission was found from SBT films, which reduces the possibility of soft error when used in the memory devices.

The Diffusion of Bismuth in Silicon

The diffusion of bismuth into silicon from a spin-on source has been investigated at a temperature range of 1050–1200°C. The concentration profile of bismuth agrees with the complementary error function, and its diffusion coefficient shows a value similar to the values of phosphorus and boron. Its activation energy is estimated to be 2.50 eV. That is much smaller than the values of phosphorus, boron and arsenic.

Changes in the surface radioactivity of lead—the effect of the diffusion of bismuth and polonium radioisotopes

Measurements and the quantitative analysis of the kinetics of the phenomenon of increasing radioactivity of lead after the scraping of the surface are presented. The growth of radioactivity concerns the α activity of polonium and to a lower degree also the β activity of bismuth. When the surface is scraped, the layer of the material near the surface is plastically deformed. Generated defects facilitate the diffusion of polonium and bismuth radioisotopes to the surface where the thermodynamic potential is lower than inside the material.

Photoconductivity and extrinsic doping of pCuInSe 2

Diffusion experiments under maximum selenium vapor pressure have been carried out on monocrystalline p-type CuInSe 2 samples. Change of resistivity after the treatments at different temperatures was investigated. Diffusion experiments were also made under bismuth and tellurium dopant atmosphere. It was found that n-type samples resulted after the bismuth diffusion, and the samples remained p-type after the tellurium diffusion. For bismuth diffusion experiments, it is believed that selenium out-diffusion is dominant during the process. Photoconductivity experiments of p-type monocrystalline CuInSe 2 samples were also performed at 77 K in the wavelength range from 0.4 to 1.6 μm. Deep etching treatment of the sample appeared to reduce the surface recombination velocity.

Diffusion and annealing effects of crystalline CuInSe2

Diffusion and annealing experiments have been made on p-type monocrystalline CuInSe2 samples grown by the directional freezing method. It was found that tellurium diffusion into CuInSe2 produced p-type conduction whereas bismuth diffusion resulted in n-type conduction. Photoconductivity experiments were also made for the first time at 77 K on p-type monocrystalline CuInSe2 samples.