Results 1 - 10 of 10244
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[en] Bulk superconductors of Pb-doped Bi-oxide system (BSCCO) dominated with the high-Tc phase have the critical transition temperature, Tc of 110 K, and the upper critical fields, Hc2 of 140 T at OK and 60 T at 77 K. A highly dense and a highly oriented microstructure is obtained by inserting an intermediate uniaxial pressing process. The critical current density, Jc at 77 K in zero field, Jc (77K,OT) of some 5000 A/cm2 can be easily obtained by this process, and the field dependence of Jc is also improved. Flexible high-Tc BSCCO ribbons with a Jc (77K,Ot) of 1850 A/cm2 have been successfully prepared by the combined process of doctor blade casting, cold rolling and sintering. Aq-sheeted multifilamentary wires with 1330 filaments and tapes with 30 filaments have also been successfully fabricated and the 36-filament tape shows a Jc(77K,OT) of 1050 A/cm2. (Auth.). 7 refs.; 7 figs
[en] The dimensionless thermoelectric figure-of-merit, ZT, of Bi2Te3 based alloys was investigated under a large temperature difference using a recently reported 'open/short circuit' measurement technique. It is shown that the measured ZT decreases with an increase in temperature difference. Theoretical analysis indicates that this dependence can be explained by taking into account the Thomson effect. An equation is obtained for a modified thermoelectric figure-of-merit which is valid for measurement over large temperature differences
[en] Here in this paper, a full-spectrum responsive vacancy-rich monolayer BiO2-x has been synthesized. The increased density of states at the conduction band (CB) minimum in the monolayer BiO2-x is responsible for the enhanced photon response and photo-absorption, which were confirmed by UV/Vis-NIR diffuse reflectance spectra (DRS) and photocurrent measurements. Compared to bulk BiO2-x, monolayer BiO2-x has exhibited enhanced photocatalytic performance for rhodamine B and phenol removal under UV, visible, and near-infrared light (NIR) irradiation, which can be attributed to the vacancy VBi-O' as confirmed by the positron annihilation spectra. The presence of VBi-O' defects in monolayer BiO2-x promoted the separation of electrons and holes. This finding provides an atomic level understanding for developing highly efficient UV, visible, and NIR light responsive photocatalysts.
[en] Bismuth tellurite is a photorefractive material for holographic data storage offering unique fixing capabilities. Important material and electro-optic properties obtained by four-wave-mixing and data storage experiments are reviewed and recent results concerning the applicability of bismuth tellurite for holographic data storage, including dynamic range, multiplexing capabilities and bit-error evaluations, are presented. Furthermore, it is demonstrated how the latest progress in growing Bi2TeO5 made this crystal a candidate for durable holographic recording media.
[en] Quantum states have been calculated analytically; the dynamics of a wave packet in a magnetic field has been investigated, and the optical absorption coefficient has been calculated for surface states in 3D topological insulators of the Bi2Te3 family. We have detected a qualitative effect of the hexagonal warping of the spectrum on the structure of wavefunctions at the Landau levels, its manifestation in the features of the wave packet dynamics in a quantizing magnetic field, as well as in the frequency dependence of the optical absorption coefficient, in which new peaks that are absent in the isotropic model of the spectrum appear depending on the polarization of the incident wave. The effects considered here can be manifested in the optical and transport experiments with topological insulators, which makes it possible to determine the parameters of their band structure.
[en] Scintillation performance of recent (2X) grown BGO is studied. Results indicate BGO to perform better than 8% 137Cs FWHM NaI(Tl) at energies 2.6 MeV and higher. Even the low energy performance of BGO is suitable for considering it in lieu of NaI(Tl) for many spectroscopic applications
[en] By numerically solving the effective continuous model of a topological insulator with parameters corresponding to the band structure of the topological insulator Bi2Se3, we analyze possible appearance of one-dimensional states in various geometries. Massless Dirac fermions are found at the edges of thin ribbons with surface oriented not only along the van der Waals gap but also in the perpendicular direction. Thick rods and slabs with surface steps host massive modes localized on surface faces. We argue that the the origin of the massive modes is due to the difference in the Dirac point energy of adjacent faces. The absence of one-dimensional states near edges of a large rectangular rod and surface steps is demonstrated. (paper)