University of Science and Technology Beijing

About: University of Science and Technology Beijing is a education organization based out in Beijing, China. It is known for research contribution in the topics: Microstructure & Alloy. The organization has 41558 authors who have published 44473 publications receiving 623229 citations. The organization is also known as: Beijing Steel and Iron Institute.

New Yellow-Emitting Whitlockite-type Structure Sr1.75Ca1.25(PO4)2:Eu2+ Phosphor for Near-UV Pumped White Light-Emitting Devices

Abstract: New compound discovery is of interest in the field of inorganic solid-state chemistry. In this work, a whitlockite-type structure Sr1.75Ca1.25(PO4)2 newly found by composition design in the Sr3(PO4)2–Ca3(PO4)2 join was reported. Crystal structure and luminescence properties of Sr1.75Ca1.25(PO4)2:Eu2+ were investigated, and the yellow-emitting phosphor was further employed in fabricating near-ultraviolet-pumped white light-emitting diodes (w-LEDs). The structure and crystallographic site occupancy of Eu2+ in the host were identified via X-ray powder diffraction refinement using Rietveld method. The Sr1.75Ca1.25(PO4)2:Eu2+ phosphors absorb in the UV–vis spectral region of 250–430 nm and exhibit an intense asymmetric broadband emission peaking at 518 nm under λex = 365 nm which is ascribed to the 5d–4f allowed transition of Eu2+. The luminescence properties and mechanism are also investigated as a function of Eu2+ concentration. A white LED device which is obtained by combining a 370 nm UV chip with commerci...

In situ synthesis of α–β phase heterojunction on Bi2O3 nanowires with exceptional visible-light photocatalytic performance

Abstract: Visible-light-responsive α–β phase heterojunction on Bi2O3 nanowire photocatalysts were prepared via a facile in situ hydrothermal process in assistance with the post-heat treatment route. The as-prepared samples were characterized by X-ray diffraction (XRD), electron microscope (EM), Brunauer–Emmett–Teller analysis (BET), X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance absorption spectra (UV–vis). XRD patterns revealed that the α–β phase heterojunction over Bi2O3 composites with the monoclinic α-Bi2O3 and the tetragonal β-Bi2O3 structure were obtained and the relative ratios between α-Bi2O3 and β-Bi2O3 can readily be tailored by the control of the reaction temperature. Within the hydrothermal temperature range, the morphology of as-prepared samples transformed progressively from two-dimensional β-Bi2O3 sheets to the α-/β-Bi2O3 nanowires junction. The exceptional photocatalytic performance of α-/β-Bi2O3 heterojunction for the degradation of cationic rhodamine B and anionic methyl orange under visible-light irradiation is superior over that of β-Bi2O3 sheets, which is ascribed to the efficient charge separation and transfer across the α-β phase junction. The phase-junction approach will open new avenues for the development of efficient photocatalysts for environmental remediation and energy conversion.

From scalable solution fabrication of perovskite films towards commercialization of solar cells

Abstract: Organic–inorganic halide perovskite solar cells (PSCs) have achieved amazing progress in terms of power conversion efficiency (PCE), rising from 3.8% to over 23.3%. Owing to perovskites’ low nucleation and crystallization activation energy (56.6–97.3 kJ mol−1), a range of low temperature and large-scale solution fabrication processes have been actively investigated for potential commercialization. Although many excellent research institutes and enterprises have emerged to advance commercialization of PSCs, the performance of devices which have large areas still lag much farther behind those of smaller lab scales. The performances of PSCs are predominantly determined by the quality of the perovskite film, which in turn, is controlled by the fabrication process. A comprehensive and in-depth understanding of the nucleation and growth process during perovskite crystallization is imperative for the further advancement of large-scale manufacturing of high quality perovskite films. This review summarizes recent advances in the commercialization of the PSCs market, and critically reviews promising large-scale solution manufacturing methods combined with their physical properties and relevant challenges with the crystallization thermodynamics and kinetics of perovskites. The hurdles and challenges of commercialization and possible approaches and solutions are discussed.

Structure evolution and photoluminescence of Lu3(Al,Mg)2(Al,Si)3O12:Ce3+ phosphors: new yellow-color converters for blue LED-driven solid state lighting

Abstract: This paper reports the development of new phosphors using the chemical unit cosubstituting solid solution design strategy. Starting from Lu3Al5O12, the Al3+–Al3+ couple in respective octahedral and tetrahedral coordination was simultaneously substituted by a Mg2+–Si4+ pair forming the Lu3(Al2−xMgx)(Al3−xSix)O12:Ce3+ (x = 0.5–2.0) series; as a result, the CeO8 polyhedrons were compressed and the emission got red-shifted from green to yellow together with the broadening. The evolution of, the unit cell, the local structural geometry as well as the optical properties of Ce3+ in these garnet creations, in response to the gradual Mg–Si substitution for Al–Al, were studied by combined techniques of structural refinement and luminescence measurements. The new composition Lu2.97Ce0.03Mg0.5Al4Si0.5O12 was comprehensively evaluated regarding its potential application in blue LED-driven solid state white lighting: the maximum emission is at 550 nm under λex = 450 nm; the internal and external quantum efficiencies can reach 85% and 49%, respectively; a 1-phosphor-converted wLED lamp fabricated using the as-prepared phosphor exhibits the luminous efficacy of 105 lm W−1, the correlated color temperature of 6164 K and the color rendering index (Ra) of 75.6. The new solid solution composition series is open for further optimization to enhance the competence for commercial consideration.