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We report on the holographic recording on photorefractive Bi2TeO5 crystals using λ = 633 nm wavelength light. We studied the behavior of this material under the action of this low photonic energy light and found out the presence of a fast and a slow hologram, both of photorefractive nature and exhibiting rather high diffraction efficiencies. The faster and the slower holograms are based on the excitation and diffusion of oppositely charged carriers (likely electrons and holes). Relevant parameters for the photoactive centers responsible for both kind of holograms were characterized using purely holographic techniques. No evidences of non-photosensitive ionic charge carriers being involved in the recording process at room temperature nor self-fixing effects were found. [ABSTRACT FROM AUTHOR]

A single layer of bismuth deposited on the Cu(100) surface forms long range ordered structural phases at various Bi density. A highly ordered c(2×2) reconstruction is accomplished at 0.5 ML, further Bi deposition induces a c(92×2)R45° structure and a subsequent p(10×10) phase related to the formation of regular dislocations arrays. The transition from a c(2×2) superstructure to the c(92×2)R45° phase is accompanied by a sudden decrease in the work function. Photoemission measurements reveal that the Bi induced states close to the Fermi level, associated to the c(2×2) phase, are strongly quenched when the arrays of dislocations are formed, while at higher binding energies, they undergo an energy shift probably due to a confinement effect. The low-energy single particle excitations and the electron dispersion of the Bi induced states of the c(2×2) phase are compared to the electronic states deduced by theoretical band structure obtained by ab initio calculation performed within the embedding method applied to a realistic semi-infinite system. [ABSTRACT FROM AUTHOR]

The optical dielectric function of bismuth germanate (Bi4Ge3O12) has been measured using spectroscopic ellipsometry and optical transmission. Analysis near the direct band edge indicates that there are at least three critical points at 4.44 (low intensity) and at 4.75 and 4.91 (high intensity). Using transmission measurements, the band gap is determined to be 4.20 eV, which is likely determined by the defects in the material. Comparisons are made with relativistic electronic structure and optical calculations based on the Engel–Vosko generalized gradient approximation. The near-absorption-edge critical points are associated with spin-orbit-split bands which significantly modify the conduction bands. [ABSTRACT FROM AUTHOR]

The thermal conductivity of individual bismuth nanowires was characterized using a suspended microdevice and correlated with the crystal structure and growth direction obtained by transmission electron microscopy on the same nanowires. Compared to bulk bismuth in the same crystal direction perpendicular to the trigonal axis, the thermal conductivity of a single-crystal bismuth nanowire of 232 nm diameter was found to be three to six times smaller than bulk in the temperature range between 100 and 300 K, and those of polycrystalline bismuth nanowires of 74–255 nm diameter are reduced by factors of 18–78 over the same temperature range. The thermal conductivity suppression in the single-crystal nanowire can be explained by a transport model that considers diffuse phonon-surface scattering, partially diffuse surface scattering of electrons and holes, and scattering of phonons and charge carriers by ionized impurities such as oxygen and carbon of a concentration on the order of 1019 cm-3. The comparable thermal conductivity values measured for polycrystalline nanowires of different diameters suggests a grain boundary scattering mean free path for all heat carriers in the range of 15–40 nm, which is smaller than the nanowire diameters. [ABSTRACT FROM AUTHOR]

Measurements of the magneto-Seebeck coefficient and magnetoresistivity of two bismuth microwire arrays having different diameters and a bulk sample were performed for applied magnetic fields between 0 and 2 T and temperatures between 50 and 300 K. The magneto-Seebeck coefficients were always enhanced as a result of controlling the phonon scattering process and the magnetoresistivity also invariably increased. The power factors in an applied magnetic field were estimated, and the power factors of the microwire arrays were found to be enhanced over the whole measurement range. By contrast, the power factor of the bulk sample was not enhanced at temperatures under 200 K. The difference in the responses of the bulk sample and the microwire arrays is strongly related to suppression of the magnetoresistivity; the suppression ratios of the magnetoresistivity of the bulk sample, which has a low aspect ratio, are smaller than those of the microwire arrays. It was experimentally demonstrated that there is an optimum magnetic field that maximizes the power factor and that the enhancement ratio of the power factor is much greater for structures that have a high aspect ratio, such as microwire arrays. This suggests that microwire arrays are suitable for enhancing the power factor by applying a magnetic field. [ABSTRACT FROM AUTHOR]

We report the results of investigation on the mechanism of dark conductivity and dielectric relaxation of Bi12GeO20 single crystals and dense ceramics. Alternating current electric characterization was performed in the temperature interval from 30 °C up to 730 °C and frequencies from 1 Hz to 13 MHz. The samples presented ohmic behavior even at high temperatures, for applied potentials up to 2.2 V. The electric conductivity of single crystals was thermally activated, with potential barriers changing from 0.75±0.05 eV to 1.4±0.2 eV at 500 °C. The same conduction mechanisms were observed for ceramic samples, with activation energies of 0.9±0.1 eV and 1.5±0.1 eV for charge transport through grains and grain boundaries, respectively. These energy values were related to defects arising from substitutional Bi3++h+ in Ge4+ sites. In the ceramic samples, the higher resistivity of the grain interfaces leads to a Maxwell–Wagner polarization of the grain boundaries due to local charge rearrangement. As a result, the overall permittivity of ceramics was higher than that observed for single crystals at frequencies corresponding to the grain boundary response. [ABSTRACT FROM AUTHOR]

Single-phase Bi1-xNdxFeO3 (BNFOx) (x=0–0.2) multiferroic ceramics were prepared to study the effects of Nd substitution on their crystal structures, Raman scattering spectra, and ferroelectric properties. Rietveld refinement of x-ray diffraction data showed a gradual change in crystal structure from rhombohedral to pseudotetragonal via triclinic with increasing x. The evolvement of Raman normal modes with increasing x suggested that such structural change is accompanied by the weakening of long-range ferroelectric order. The simultaneous occurrence of abrupt mode evolvement and ferroelectric-paraelectric transition in BNFOx=0.175 and BNFOx=0.2 was explained according to the change of Bi–O covalent bonds as a result of the decline in the stereochemical activity of the Bi lone electron pair at 0.175<=x<=0.2. [ABSTRACT FROM AUTHOR]

The magneto-Seebeck coefficient and magnetoresistivity of a polycrystalline bismuth microwire array were measured under magnetic fields of 0–2 T and at temperatures of 50–300 K. To avoid the influence of contact resistance between the wire array and the electrodes, bulk bismuth was used for the electrodes. In the absence of a magnetic field, the Seebeck coefficient and resistivity were -76 μV/K and 1.8 μΩ m at 300 K, respectively. The magneto-Seebeck coefficient for the wire array increased with the application of an external magnetic field, attributable to the precise control of impurities and carrier scattering process in the fabrication of the wire array. The phonon drag effect was observed below 100 K, with a corresponding increase in the magneto-Seebeck coefficient under high magnetic fields. However, the magnetoresistivity was also raised under higher magnetic fields, detracting from the thermoelectric properties. Through analysis of the power factor, the optimum magnetic field was determined for each temperature, revealing a trend for the optimum magnetic field to increase with temperature. The power factor was improved by a maximum factor of 1.12, achieved at 200 K and 0.25 T. Further improvements appear to be possible by eliminating the bulk bismuth employed for the electrodes. [ABSTRACT FROM AUTHOR]

Reports on the effect of surface treatments on the dynamic conductance curves of Au-Bi[sub2]Sr[sub2]CaCu[sub2]O[sub8+δ] point contact junctions of variable junction conductances. Performance of point contact junctions in liquid helium; Method used to grow the bismuth single crystals; Sequence in which the surface treatment of the sample was done before making the point contact; Results and discussion.

Deals with a study which analyzed the thermally stimulated current (TSC) in bismuth germanium oxide (BSO) crystals. Effect of field strength on BSO; Influence of ultraviolet excitation temperature on TSC; Temperature dependence of trap density.

Presents a study which analyzed dark decays of photorefrative gratings observed in bismuth[sub 12]silicon oxide [sub 20] crystal. Model for nonexponential dark decays; Experiments on dark decays in bismuth[sub 12]silicon oxide [sub 20] crystal; Conclusion.

Sapphire and Bismuth crystals are used as fast neutrons and high energy gammas filters for several nuclear facilities such as Prompt Gammas Activation facility, Neutron diffraction, Neutron Imaging around research reactors. In this paper, we will focus on phonon frequency distributions (density of states) generation. As a tool, we used the ifit mccode, PhonoPy and Quantum-expresso package. The obtained information's were enfolded in LEAPR module of the NJOY 2016 code to prepare the scattering law S(α,β) at various temperatures. [ABSTRACT FROM AUTHOR]

Highlights • A Bi doped GYAP crystal with high optical quality was successfully grown by the Czochralski method. • An intense and broadband Near-IR (NIR) 900–1700 nm emission in Bi:GYAP crystal was observed for the first time. • Bi:GYAP crystal may be an attractive host for developing wide tuning range and ultrashort lasers at around NIR wavelength. Abstract A Bi doped Gd 0.1 Y 0.9 AlO 3 (GYAP) crystal with high optical quality was successfully grown by the Czochralski method. An intense and broadband Near-IR (NIR) 900–1700 nm emission in Bi:GYAP crystal was observed for the first time. By analyzing the emission and excitation spectra of the Bi:GYAP crystal, the optical properties were researched in details. It is found that the two broadband NIR luminescence emission mainly peaking at 1005 and 1565 nm are ascribed to two different Bi+ related centers distinct sites. Moreover, the visible emission peaking at 430, 470, 515 and 630 nm are also obtained under the excitation at 250 nm, which show that there exist multiple valence states of luminescence in the mixed crystal. All these results show that Bi:GYAP crystal may become an attractive host for developing wide tuning range and ultrashort lasers at around NIR wavelength. [ABSTRACT FROM AUTHOR]

This study aims to find out the crucial variations in the mechanical performance and characterization of Bi- 2223 superconducting compounds with the diffusion annealing temperatures interval 650 °C-850 °C by means of Vickers hardness measurements exerted at the different applied indentation test loads (0.245 N- 2.940 N) and derived theoretical findings. All the experimental results and theoretical evidences showed that the mechanical characterization and performances improve with the increment in the diffusion annealing temperature up to 700 °C due to the development in structural properties. Namely, the optimum annealing temperature of 700 °C resulting in the optimum penetration of Ni impurities into both the superconducting grains and over the grain boundaries develops the crystallinity of Bi-2223 crystal structure. In other words, the surface energy related to the crack-initiating omnipresent flaws, void/crack propagation and dislocation movement reduces due to the augmented critical stress value. In this respect, the diffusion annealing temperature of 700 °C develops the mechanical durability, stiffness, ideal fracture and flexural strength. However, after the certain diffusion annealing temperature value of 700 °C, the crystallinity tends to degrade considerably and in fact dwelling in the worst crystal structure for 850 °C annealing temperature. Accordingly, the initial crack growths, sizes of crack-producing flaws, void/crack propagation and dislocation movement in the copper-oxide consecutively stacked layers reach much more rapidly to the critical speeds due to the increased stress amplification so that the Bi-2223 compound with the augmented brittle behavior breaks at even lower test load. Moreover, it is observed that the presence of optimum nickel impurities in the crystal structure strengthens the standard indentation size effect behavior. [ABSTRACT FROM AUTHOR]

We propose a method for calculating nonstationary heat fluxes using the electric-response signal of a sensor based on anisotropic bismuth single-crystal thermoelements. Using this method, it is possible to approximately calculate the heat flux during a period of time from ∼1 μs to the attainment of a stationary thermal regime. Tests showed that the monitoring of short-term (t ∼ 1-10 ms) heat fluxes by bismuth-crystal-based sensors with a crystal length to thickness ratio of above 25 ensures a calculation error not exceeding several percent. [ABSTRACT FROM AUTHOR]

In the present study, reduction in the linear density of twinning dislocations resulting from the simultaneous application of high-density electric current pulses (40 A/mm² for 400 µs) and constant magnetic field (with induction in 0.2 T) to bismuth crystals has been found. Current pulses and constant magnetic field were applied to the specimen after the deformation was introduced by a concentrated load and pileups of twinning dislocations were created. It has been clearly shown that the decrease in the linear density of twinning dislocations results in the elongation of the deformation twins. This effect occurs despite the increase of the number of twinning dislocations with an increase in the concentrated load. The experimental facts are in good accord with the modern concept of the electroplastic effect. [ABSTRACT FROM AUTHOR]

Finite-size effects in Bi lines of cross section 3 μmxw, where w=8-120 μm, have been studied. The lines were made by optical lithography followed by electrodeposition. At T=5 K, the magnetoresistance (MR) decreases monotonically with decreasing line width of the Bi films, from 44 000% at w=120 μm to 4000% at w=8 μm in a field of 50 kOe. The decrease of the MR with decreasing linewidth is due to a decrease of the size-limited effective-mean-free path. At low temperatures, both the resistivity and the magnetoresistivity show a strong dependence on w, whereas at room temperature, they are independent of w. The MR at room temperature remains at about 230% for linewidths w=8-120 μm at 50 kOe. This demonstrates that microstructured Bi lines can be made for field-sensing applications without compromising their MR characteristics. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Tensile tests were performed on bismuth single crystals in the [0001] ( c-axis), [2 $$\bar{1}\bar{1} $$ 0] ( a -axis), [10 $$\bar{1} $$ 0] and [1 $$ \bar{1} $$ 00] directions of bismuth single crystals to investigate the influence of temperature on plastic deformation behavior. The plastic deformation at 298 K was caused by slip on the secondary slip system in the [0001] direction, or by twinning and slip deformation in twins subsequent to the twining deformation in the [2 $$\bar{1}\bar{1} $$ 0] direction. Those mechanisms resulted in ductile characteristics in tension. Only deformation twinning, however, was observed along the [10 $$\bar{1}$$ 0] and [1 $$\bar{1} $$ 00] directions, which lead to brittle fracture. At elevated temperature (423 K), deformation twinning was not found to occur along any of the examined directions. Crystallographic slip was the predominant deformation mechanism along the [2 $$\bar{1}\bar{1} $$ 0], [10 $$\bar{1} $$ 0] and [1 $$\bar{1} $$ 00] directions at 423 K. This is attributed to the activation of the {1 $$\bar{1} $$ 02}<11 $$\bar{2} $$ 0> or {1 $$\bar{1} $$ 02}<1 $$\bar{1} $$ 0 $$\bar{1} $$ > slip system which are inactive at 298 K. Along the [0001] direction at 423 K, the {0 $$\bar{1} $$ 11}<10 $$\bar{1} $$ 1> was active and its critical resolved shear stress ( τ ) does not coincide with that corresponding to the {1 $$\bar{1} $$ 02}<11 $$\bar{2} $$ 0> and {1 $$\bar{1} $$ 02}<1 $$\bar{1} $$ 0 $$\bar{1} $$ > systems. Therefore, it can be concluded that difference in τ between slip systems causes anisotropy in mechanical behavior at 423 K. [ABSTRACT FROM AUTHOR]

The neutral, anionic and cationic bismuth clusters with the size n up to 14 are investigated by using B3LYP functional within the regime of density functional theory and the LAN2DZ basis set. By analysis of the geometries of the Bi ( n = 2-14) clusters, where cationic and anionic bismuth clusters are largely similar to those of neutral ones, a periodic effect by adding units with one to four atoms into smaller cluster to form larger cluster is drawn for the stable structures of bismuth clusters. An even-odd alteration is shown for the properties of the clusters, such as the calculated binding energies and dissociation energies, as well as frontier orbital energies, electron affinities, ionization energies. All the properties indicate that the Bi4 cluster is the most possible existence in bismuth-containing materials, which supports the most recent experiment. The orbital compositions, infrared and Raman activities and the ultraviolet absorption of the most possible tetramer bismuth cluster are given in detail to reveal the periodic tendency of adding bismuth atoms and the stability of tetramer bismuth cluster. [ABSTRACT FROM AUTHOR]

Presents information on inelastic electron tunneling experiments performed in bismuth telluride semiconductor crystals. Details on methodology used to conduct experiments; Indication of results; Discussion on findings.

Presents information on a study which measured the distribution of the trapped flux in a miniaturized flux-gate magnetometer for BiSrCaCuO high-T[sub c] superconductor. Description of a proposed lightweight and high-performance magnetic shield square loop magnetic materials with applied magnetic shaking; Methodology of the study; Results and discussion.

Investigates the electrical and magnetic properties of the superconducting oxides with nominal composition lead-doped bismuth-strontium-calcium-copper-oxygen superconductors prepared from polymeric precursors. Dependence of the superconducting transition temperature on heat treatment time; Measurement of electrical resistivity and critical current density.

Quantum dot sensitized solar cells (QDSSCs) were fabricated using low cost Bi 2 S 3 nanocrystals and CdS quantum dots. Au nanorods (NRs) were synthesized by a seed-growth method and Au NRs were deposited over a TiO 2 /Bi 2 S 3 /CdS electrode by a drop casting method. The Au NRs increased the light absorption of the photoanode, TiO 2 /Bi 2 S 3 /CdS/Au NRs, through plasmonic effects. CdS QDs absorb in the visible region, Bi 2 S 3 nanocrystals absorb almost in the near infrared (NIR) region, and Au NRs show near field plasmonic effects and are also capable of hot electron transfer, and therefore this combined electrode is expected to deliver high power conversion efficiencies (PCEs). Upon illumination, electron-hole pairs are generated in CdS and Bi 2 S 3 , and the excited electrons are transferred to TiO 2 directly or via the equilibrated Fermi level induced by Au NRs. QDSSCs with different photoanode compositions were fabricated with functionalized MWCNTs as a counter electrode and a Na 2 S solution as an electrolyte. Among all cells, the highest PCE achieved for the champion cell is 4.26%, with a TiO 2 /Bi 2 S 3 /CdS/Au NRs photoanode, with an active area of 0.13 cm 2 , and 3.83%, when the area was increased to 0.51 cm 2 . Retention of a moderately high efficiency upon scale-up indicates that the photoactive material packing over the substrates requires some more improvement to match the values attained when the cells were fabricated over small areas. Compared to CdS QDs, Bi 2 S 3 nanocrystals are less toxic, and have a bandgap of 1.55 eV. The cell with a TiO 2 /Bi 2 S 3 /Au NRs photoanode also shows a high PCE of 2%. The use of Bi 2 S 3 nanocrystals to yield high efficiency QDSSCs is a small but a vital step towards developing cells with low toxicity. [ABSTRACT FROM AUTHOR]

Bi 3 NbO 7 single crystal nanosheets have been fabricated through a solvothermal method. The characterization results show that the phase and morphology could be controlled by adjusting reaction parameters such as urea content and pH value. Under appropriate conditions, Bi 3 NbO 7 nanosheets with square pores can be obtained. These novel porous nanosheets are potential photocatalysts with the narrow band gap which allows to utilizing visible light irradiation for photocatalysis. The results of the photocatalytic tests exhibit the porous ones have higher activity than those nonporous ones. After four batches of photodegradation of Rhodanmine B (RhB), the samples still had stable porous structure and no deactivation. [ABSTRACT FROM AUTHOR]

In this study, graphene-decorated 3D flower-like BiVO 4 photocatalyst coupling with highly reactive (040) facets was synthesized by a facile alkaline solvothermal route. With the addition of graphene oxide (GO), the size of the subunits composing the 3D flower-like dramatically decreases, while the size of the flower is almost unchanged. Fascinatingly, the introduction of GO in the synthesis medium facilitates the preferential crystal growth of the 3D BiVO 4 photocatalyst along its (040) facets. The as-prepared 3D BiVO 4 /graphene composites with the exposed (040) facets exhibits the enhanced activity in the visible-light photocatalytic oxidation (PCO) of NO (∼400 ppm), wherein the BiVO 4 /graphene (2.4 wt%) composite displays the highest photoactivity of PCO of NO. The improved photocatalytic performance was found to be associated with the synergetic effects of the exposed photogenerated electron-rich (040) facets of BiVO 4 and the enhanced electronic conductivity caused by the graphene, and more significantly, the interaction between BiVO 4 and graphene sheets which reduces the recombination of photoinduced charge carriers. The present study points out that the role of graphene is not only a capping agent to design the highly reactive (040) facets, but also a catalyst promoter for the photocatalytic performance, resulting in an enhanced photoactivity. [ABSTRACT FROM AUTHOR]

We have investigated the source of dislocations generated during growth and subsequent cooling of quasi-monocrystalline silicon. Bi-crystals of silicon separated by ∼5.2° tilt small angle grain boundary have been directionally solidified at two different pulling rates, i.e., 3 and 13 μm s−1. We observe higher density of grain boundary-associated dislocations at the ingot pulled at a lower rate. This observation is explained by the impact of oxygen precipitation behavior at the grain boundary. [ABSTRACT FROM AUTHOR]

In the present work, we investigate the wear mechanisms of a Cu bi-crystal containing a random high angle grain boundary by means of molecular dynamics simulations. The underlying deformation behavior of the material is analyzed and further related to the observed characteristics of mechanical response and resulting morphology of the worn surface. In particular, the grain boundary-associated mechanisms are characterized by advanced analysis techniques for lattice defects. Our simulation results indicate that in addition to dislocation slip and dislocation-grain boundary interactions, grain boundary migration plays an important role in the plastic deformation of Cu bi-crystal. It is found that the wear behavior of Cu depends on the crystallographic orientation of the worn surface and can be altered quite significantly by the presence of a grain boundary. [ABSTRACT FROM AUTHOR]

Different Au-Ag-Cu samples have been studied by mechanical spectroscopy. Both polycrystals and bi-crystals show a relaxation peak at 800 K, accompanied by an elastic modulus change. Since this peak is absent in single crystals it is related to the presence of grain boundaries. Molecular dynamics simulations reveal two microscopic mechanisms, when a shear stress is applied onto a Σ5 grain boundary: at 700 K, the boundary migrates perpendicularly to the boundary plane under an external stress. At 1000 K, only sliding at the boundary is observed. These two mechanisms acting in different temperature intervals are used to model the mechanic response of a polycrystal under an applied stress. The models yield expressions for the relaxation strength Δ and for the relaxation time τ as a function of the grain size. A comparison with the mechanical spectroscopy measurements of polycrystals and the bi-crystals show that the grain boundary sliding model reproduces correctly the characteristics of the grain boundary peak. [ABSTRACT FROM AUTHOR]

This present work studies the effects of grain boundaries (GBs), notches and temperature on the mechanical properties of silicon (Si) nanofilms via molecular dynamics simulations. Both ∑25 (7 1 0)〈0 1 0〉 tilt and ∑25(0 0 1)〈0 0 1〉 twist GBs are considered. It is found that the single-crystalline Si nanofilm has relatively low fracture strength of ∼11.6 GPa at room temperature, and fracture occurs through the dislocation sliding mechanism regardless of the existence of notches. At the same temperature, the bi-crystalline Si generally has lower fracture strength than that of the single-crystalline due to the presence of GBs, which changes the crystallographic orientation of the Si nanofilms. Moreover, strength of the bi-crystalline Si depends on the type of the GBs, and it fractures through either the dislocation sliding or cleavage mechanism, depending on the presence of notches. The temperature reduces the fracture strength of the nanofilms but does not change the failure mechanism. [ABSTRACT FROM AUTHOR]

The origin of intrinsic photoluminescence (PL) in the set of Bi-containing phosphate, molybdate and tungstate crystals is analyzed in complex experimental and computational studies. The PL properties of polycrystalline powder samples of BiPO4, K3Bi5(PO4)6, K2Bi(PO4)(MoO4), K2Bi(PO4)(WO4) and K5Bi(MoO4)4 crystals synthesized by spontaneous crystallization method are studied under excitations in the VUV and UV region of photon energies (3.5-14 eV) at T = 8-300 K. The electronic band structures of the crystals are calculated by the Full-Potential Linear Augmented Plane Wave Method. The values of band gaps Eg of studied compounds are estimated from diffuse reflectance and PL excitation spectra. Calculations indicate that all studied crystals except K5Bi(MoO4)4 are indirect-gap materials. It is found that the Bi 6s and Bi 6p states contribute respectively at the tops of the Valence bands and the bottoms of the Conduction bands of all studied compounds. Each studied compound reveals several (at least two) PL emission components which undergo complete quenching below room temperature. Under nitrogen laser excitation with λex = 337.1 nm, all studied crystals reveal single-exponential decay of PL signal with decay constants τ in 3-35 µs range. It is assumed that the high-energy PL components of BiPO4, K3Bi5(PO4)6 and K2Bi(PO4)(MoO4) (peaking in the blue and violet regions) originate from ³P1 → ¹S0 radiative transitions in Bi3+ ions. The red PL components of K2Bi(PO4)(MoO4) and K5Bi(MoO4)4 have the MoO42--related origin. The red PL component of K2Bi(PO4)(WO4) presumably originates from the molybdenum impurities which form MoO42- emission centers in the phosphate-tungstate host. [ABSTRACT FROM AUTHOR]

Pure and Sm-doped α-BiO micro crystals (rods) have been prepared using modified sol-gel synthesis under mild reaction temperature (~80 °C). Crystal structure, optical absorption, luminescence and phonon properties has been investigated using powder X-ray diffraction, UV-Vis, photoluminescence, Raman and infrared spectroscopy. Crystalline α-phase of microstructures is identified using XRD and spectroscopic measurements. Luminescence properties of the micro rods has been investigated for the pure and Sm-doped BiO samples, and it is observed a strong luminescence which corresponds to band gap of 3.4 eV along with the usual visible luminescence exhibit by the BiO. Raman spectra of the synthesized microstructures reveal various phonon vibration modes of Bi and BiO. [ABSTRACT FROM AUTHOR]

A novel Ag-Bi nanoparticle has been prepared via a facile precipitation approach. The nanoparticle could achieve purification of contaminated water without supplements and exhibited much higher activity compared to other popular nanoparticles (e.g. nZVI). The excellent performance of Ag-Bi was due in part to a large production of *OH radicals. [ABSTRACT FROM AUTHOR]

Highlights: [•] Complete characterization of three bismuth–dithio complexes. [•] Three well refined single crystal X-ray structures. [•] The CShM evaluation correlated to distortion in geometry. [•] Bond valence sums confirm the trivalent nature of bismuth. [•] Nano bismuth sulfide characterized by PXRD, SEM, EDX and HRTEM. [ABSTRACT FROM AUTHOR]

Highlights: [•] We investigate a Ag-sheathed Bi-2223 wire by low-voltage aberration-corrected STEM. [•] Atomic displacements enable each layer to be continuous at edge grain boundaries. [•] The grains are terminated with deficient (Bi,Pb)–O layers at the other boundaries. [•] EELS mapping visualizes atomic columns in the intergrowth of Bi-2212 and 2234 phases. [•] HAADF analysis shows modulation of the occupancy of the (Bi,Pb) sites along [110]. [ABSTRACT FROM AUTHOR]

We describe a laboratory experiment that serves as an introduction to solid-state and materials science, a topic that requires additional attention in the undergraduate chemistry laboratory curriculum. The experiment illustrates the long-range translational order, crystal growth, and the macroscopic manifestations of that order. This is demonstrated through the preparation and characterization of large, well-formed bismuth crystals, an aesthetically pleasing product. The characterization of the grown bismuth crystals involves determination of melting point and enthalpy of fusion via differential scanning calorimetry. The temperature dependence of the electrical resistance of grown bismuth crystals is also measured. Students are encouraged to consider the effect of metallic bonding interactions on the melting of the crystal samples and on their ability to conduct electricity. Students also analyze how the impurities influence the melting point and the electrical properties. The experiment is suitable for use in the third- or fourth-year undergraduate laboratory and is performed by students in one four-hour session. The experiment could be adapted to two laboratory sessions, with the first two-hour session covering crystal growth, and the second two-hour session focused on thermal and electrical characterization. [ABSTRACT FROM AUTHOR]

Highlights: [•] We introduce an electrooptic figure of merit for the photon CAM-to-OAM conversion. [•] The effective EO coefficients for the SAM-to-OAM conversion are derived. [•] Bi12TiO20 crystals reveal the highest figure of merit. [•] The efficiency of the SAM-to-OAM conversion is measured experimentally. [ABSTRACT FROM AUTHOR]

The magneto-transport properties of thin single crystal Bi films epitaxial grown on Si (111)-7 × 7 surfaces are investigated systematically as functions of film thickness (5–55 nm) and temperature. Under a perpendicular magnetic field, the positive magnetoresistance (PMR) effect is normally found, and its curve shapes are evolved systematically with film thickness. In contrast, under parallel magnetic fields the PMR effect observed for thinner Bi films develops into the negative magnetoresistance effect with the increasing magnetic field for the thicker Bi film. Our analysis indicates that there exists strong competition between the weak anti-localization effect in the surface states and the weak-localization effect in the bulk states of the Bi film, which induces the anomalous changes in the parallel magneto-resistance curves. The temperature-dependent experiments further demonstrate that the surface state plays an important role in the magneto-transport process of Bi films. [ABSTRACT FROM AUTHOR]

A detailedaccount of the crystal-growth technique and real structure effectsof the first 3D weak topological insulator Bi14Rh3I9= [(Bi4Rh)3I][BiI4]2is given. As recently shown, this compound featuresdecorated-honeycomb [(Bi4Rh)3I]2+sheets with topologically protected electronic edge-states and therebyconstitutes a new topological class. Meticulous optimization of thesynthesis protocol, using thermochemical methods, yielded high-qualitycrystals of Bi14Rh3I9suitable forthe experimental characterization of the structural as well as topologicalproperties. Insightful information about the crystal structure, itspseudosymmetry, and the thereby caused stacking disorder and twinningphenomena, obtained by X-ray diffraction and TEM studies, is crucialfor an adequate theoretical modeling of coupling between the topologicallynontrivial sheets. As demonstrated here, Bi14Rh3I9is not an exotic anomaly, but a stable, structurallywell-defined bulk material, which can be used for gaining experimentalknowledge about the yet poorly investigated class of weak 3D topologicalinsulators. It could equally foster the synthesis and understandingof related compounds with the bismuth-based decorated-honeycomb sheets. [ABSTRACT FROM AUTHOR]

CdTe crystals of two types have been grown by the vertical Bridgman method: (i) crystals doped with Bi to ∼10 cm and (ii) double-doped (Bi + Cl) crystals with a Bi concentration of ∼10 cm and a Cl concentration of ∼10 cm. The temperature dependences of the resistivity, photoconductivity, and low-temperature photoluminescence are investigated for the crystals grown. Analysis has shown that doping with Bi (crystals of the first type) leads to compensation of the material. The resistivity of the CdTe:Bi samples at room temperature, depending on the doping level, is varied in the range of 10-10 Ω cm. The hole concentration is determined by the acceptor level at E + 0.4 eV in lightly doped CdTe:Bi samples and by the deep center at E + 0.72 eV in heavily doped CdTe:Bi samples. Double doping leads to inversion of the conductivity type and reduces the resistivity to ∼1 Ω cm. Heavily doped CdTe:Bi crystals and double-doped crystals exhibit the presence of acceptors with an ionization energy of 36 meV, which is atypical of CdTe. [ABSTRACT FROM AUTHOR]

Abstract: Generation of two higher-order diffraction beams in two-wave mixing in transmission geometry have been analyzed theoretically in photorefractive cubic crystal of 23 symmetry, BSO (Bismuth Silicon Oxide) and considering its optical activity as one of the important parameter. Results are shown graphically by solving coupled wave equations using fourth-order Runge–Kutta method. The effect of polarization state of pump beam, optical activity, off-Bragg parameter, coupling coefficients, absorption and thickness of crystal has been analyzed on the beam intensities and their respective polarizations. It has been observed that as the value of the off-Bragg parameter reduces the transfer of energy to the higher-order beams increases. It has been also observed that by selecting proper input beam polarization and crystal thickness, diffracted beam intensity and its polarization could be controlled considerably. It has also been seen that by controlling input pump beam polarization, particular higher-order beam can be selectively amplified. [Copyright &y& Elsevier]

Relations determining the contribution of the inverse flexoelectric effect to the photorefractive response have been determined for the case of the interaction of a steady pump wave conserving left-hand circular polarization with a phase-modulated signal wave that has circular polarization of the opposite sign on the input face of a crystal that has the (100) orientation and symmetry group 23. The experimental studies of such an interaction in a BiTiO0:Fe,Cu crystal make it possible to estimate its flexoelectric coefficient as f = 5.3 nC/m. [ABSTRACT FROM AUTHOR]

Nanocrystals of europium-doped bismuth tungstate (Bi2WO6:Eu) have been prepared by solvothermal method at 180 °C for 2 h. The products were characterised by powder X-ray diffraction, energy dispersive X-ray analysis, scanning electron microscopy and UV-visible diffuse reflectence spectra. The photocatalytic activity of all the samples was evaluated by degradation of Rhodamine B under sunlight irradiation. The photocatalytic activity of Eu-doped Bi2WO6 shows higher photocatalytic activity in the presence of H2O2 and explained. [ABSTRACT FROM AUTHOR]

Unveiling the nature of the bosonic excitations that mediate the formation of Cooper pairs is a key issue for understanding unconventional superconductivity. A fundamental step toward this goal would be to identify the relative weight of the electronic and phononic contributions to the overall frequency (Ω)-dependent bosonic function, Π(Ω). We performed optical spectroscopy on Bi2Sr2Ca0.92Y0.08Cu2O8+δ crystals with simultaneous time and frequency resolution; this technique allowed us to disentangle the electronic and phononic contributions by their different temporal evolution. The spectral distribution of the electronic excitations and the strength of their interaction with fermionic quasiparticles fully account for the high critical temperature of the superconducting phase transition. [ABSTRACT FROM AUTHOR]

Abstract: Grain boundaries in thin Bi(110) films deposited on highly oriented pyrolytic graphite are investigated at atomic resolution using scanning tunnelling microscopy and high-resolution transmission electron microscopy. We find preferred misorientation angles Θ equal to 216°, 87°, 49°, 31°, 20°, 12° and 5°, the majority of which can be classified as large-angle boundaries. We find good agreement between the experimental results and a model of the tilt [110] grain boundary developed here. A method for estimating the surface unit cell based on measurement of dihedral angle in low-resolution images is also developed. [Copyright &y& Elsevier]

Abstract: The limits of metal cation substitution and distribution in the sequence Bi2Fe4O9–Bi2Mn4O10 have been investigated by solid state synthesis, X-ray powder diffraction, and Mössbauer spectroscopy. Rietveld refinements conducted for the entire range along the join indicate the structures are orthorhombic with space group Pbam, with partial transition-metal site disorder confirmed and detailed by Mössbauer spectroscopy. Single-phase regions are found near each end-member and a two-phase region is observed at intermediate compositions, extending from about x=1 to 3, according to the general formula of the mixed crystals Bi2Fe4−x Mn x O10−δ . An incorporation of Mn at octahedral sites replacing Fe is taken into account for the Bi2Fe4O9-related side of the system. Charge compensation is believed to be effected by addition of O, which gives rise to the formation of FeO5 pyramids. At the Bi2Mn4O10-related side of the system, substitution of pyramidal Mn3+ by Fe3+ is envisaged. [Copyright &y& Elsevier]