- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Synthesis of RE6?xCa1.5xSi11N20O (RE = Yb, Lu; x ≈ 2.2) with Lu6?xCa1.5xSi11N20O:Ce3+ Offering Interesting Spectral Properties ?for Yellow-Emitting Phosphors in 1pcLEDs
摘要： The oxonitridosilicates RE6?xCa1.5xSi11N20O (RE = Yb, Lu; x ≈ 2.2) were synthesized starting from REF3, CaH2, and “Si(NH)2” in a radiofrequency furnace at 1600 or 1400 °C, respectively. The crystal structure was solved and refined from single-crystal X-ray diffraction data of dark red Yb6?xCa1.5xSi11N20O crystals in the trigonal space group P31c (no. 159) with a = 9.8281(10), c = 10.5968(13) ? and Z = 2. The structure represents a filled variant of the Er6Si11N20O structure type, in which the charge difference caused by substitution of trivalent Yb3+ with bivalent Ca2+ is balanced by occupation of an additional third cation site. Synthesis of Lu6?xCa1.5xSi11N20O:Ce3+ resulted in a yellow powder with yellow luminescence. Powder X-ray data were analyzed by Rietveld refinement based on the crystal data obtained from Yb6?xCa1.5xSi11N20O. The Ce3+ doped compound exhibits a broad emission (fwhm ≈ 168 nm / ≈ 5100 cm?1) with a maximum at λem ≈ 565 nm. The emission extends more in the red spectral range compared to YAG:Ce3+, thus making it an interesting phosphor for warm-white single phosphor converted light emitting diodes (1pcLED) with an improved color rendering index.
关键词： Structure elucidation,Solid-state reactions,X-ray diffraction,Luminescence,High-temperature chemistry
更新于2025-09-11 14:15:04
-
High Temperature and Power Dependent Photoluminescence Analysis on Commercial Lighting and Display LED Materials for Future Power Electronic Modules
摘要： commercial light emitting diode (LeD) materials - blue (i.e., inGan/Gan multiple quantum wells (MQWs) for display and lighting), green (i.e., inGan/Gan MQWs for display), and red (i.e., Al0.05Ga0.45in0.5p/Al0.4Ga0.1in0.5P for display) are evaluated in range of temperature (77–800) K for future applications in high density power electronic modules. the spontaneous emission quantum efficiency (QE) of blue, green, and red LED materials with different wavelengths was calculated using photoluminescence (pL) spectroscopy. the spontaneous emission Qe was obtained based on a known model so-called the ABc model. this model has been recently used extensively to calculate the internal quantum efficiency and its droop in the III-nitride LED. At 800 K, the spontaneous emission quantum efficiencies are around 40% for blue for lighting and blue for display LED materials, and it is about 44.5% for green for display LED materials. The spontaneous emission QE is approximately 30% for red for display LED material at 800 K. The advance reported in this paper evidences the possibility of improving high temperature optocouplers with an operating temperature of 500 K and above.
关键词： high temperature,LED materials,power electronics,quantum efficiency,photoluminescence
更新于2025-09-11 14:15:04
-
Construction of high <i>T</i> <sub/>c</sub> BiScO <sub/>3</sub> -BiFeO <sub/>3</sub> -PbTiO <sub/>3</sub> and its enhanced piezoelectric properties by sintering in oxygen atmosphere
摘要： The high-temperature piezoelectric ceramics 0.36[(1 ? x)BiScO3-xBiFeO3]-0.64PbTiO3 was constructed by introducing BiFeO3 with a high Curie temperature (Tc ～ 830 °C) in the 0.36BiScO3-0.64PbTiO3 binary system. In terms of microstructure, low-melting BiFeO3 plays a role as a sintering aid, lowering the sintering temperature of the ceramic and signi?cantly increasing the grain size. At the same time, the crystal structure shifts from the initial morphotropic phase boundary to the tetragonal phase side, and the Tc increased gradually with increasing BiFeO3 content. Under the conventional air atmosphere sintering conditions, the Tc of the sample with x = 0.3 can reach ～500 °C, and the piezoelectric constant d33 is 125 pC/N. Compared with that, the d33 of the same composition sample sintered in an oxygen atmosphere is increased to 165 pC/N, which is mainly due to the decrease in the content of oxygen vacancies that helps to increase poling electrical ?eld. Moreover, the oxygen-sintered specimen exhibits an excellent thermal stability in a wide temperature range from room temperature to 450 °C, indicating that it is a promising candidate for ultra-high-temperature piezoelectric devices applications.
关键词： high-temperature piezoelectric ceramics,thermal stability,BiScO3-BiFeO3-PbTiO3,sintering in oxygen atmosphere,piezoelectric properties
更新于2025-09-11 14:15:04
-
Comparison of HPHT and LPHT annealing of Ib synthetic diamond
摘要： Defect transformations in type Ib synthetic diamond annealed at a temperature of 1870 °C under stabilizing pressure (HPHT annealing) and in hydrogen atmosphere at normal pressure (LPHT annealing) are compared. Spectroscopic data obtained on the samples before and after annealing prove that the processes of nitrogen aggregation and formation of nitrogen-nickel complexes are similar in both cases. Essential differences between HPHT and LPHT annealing are stronger graphitization at macroscopic imperfections and enhanced lattice distortions around point defects in the latter case. The lattice distortion around point defects is revealed as a considerable broadening of zero-phonon lines of "soft" (vacancy-related) optical centers. It was found that LPHT annealing may enhance overall intensity of luminescence of HPHT-grown synthetic diamonds.
关键词： nitrogen aggregation,graphitization,low pressure high temperature annealing,synthetic type Ib diamond,spectral broadening,high pressure high temperature annealing
更新于2025-09-10 09:29:36
-
Modeling of Quench Behavior of YBa<formula><tex>$_{2}$</tex></formula>Cu<formula><tex>$_{3}$</tex></formula>O<formula><tex>$_{7-\delta}$</tex></formula> Pancake Magnets and Distributed Temperature Sensing-based Quench Detection for Operating Temperature 30 K - 77 K
摘要： A two-dimensional/three-dimensional (2-D/3-D) mixed electrothermal model is proposed for the simulation of quench behavior of high-temperature superconducting (HTS) pancake magnets, where a 2-D electrothermal model is proposed to simulate the YBa2 Cu3 O7 -δ (YBCO) subcoil and is coupled with the remaining parts of the YBCO magnet, which are treated as 3-D homogeneous coils. For operating temperature from 30 to 77 K, the quench behavior of four YBCO pancake coils (two Kapton-insulated coils and two TiO2 -insulated coils) are simulated. Thermal equilibrium states are found for both Kapton- and TiO2 -insulated coils. The thermal conductivity of insulating materials (Kapton, TiO2 ) significantly affects the equilibrium temperature profiles (ETPs) and the minimum quench energy (MQE), especially for relatively high operating temperature (e.g., 65–77 K). The distributed-temperature-sensing-based (DTS-based) quench detection criterion can be established on ETPs. The effect of the thickness of insulating materials on ETPs and MQEs is relatively weak, especially under relatively low operating temperature. The key parameters of ETP-based quench detection criterion, such as the reference temperature, the peak temperature, and the minimum normal zone size, are obtained for the operating temperature from 30 to 77 K.
关键词： quench detection criterion,Distributed temperature sensing (DTS),high-temperature superconducting (HTS) magnet,quench simulation,minimum quench energy (MQE)
更新于2025-09-10 09:29:36
-
High-Periphery GaN HEMT Modeling up to 65 GHz and 200°C
摘要： In this article, we report on the temperature-dependent GaN HEMT behavior. To evaluate the potentialities of this kind of active solid-state electronic device at its best, the experiments are performed at extreme operating conditions. As a case study, we consider a large 0.25-μm GaN HEMT with a gate periphery of 1.5 mm, providing a high dissipated power of 5.1 W. The tested semiconductor device is characterized by measuring scattering parameters at high frequencies up to 65 GHz and at high ambient temperature up to 200°C. To assess the impact of the thermal effects on high-frequency GaN HEMT performance, an equivalent circuit is analytically extracted and then used to determine the main RF figures of merit. The achieved experimental results show evidence that the increase of the temperature causes a significant degradation in device performance.
关键词： scattering parameter measurements,high-power,GaN HEMT,high-temperature,Active solid-state electronic device,millimeter-wave frequency
更新于2025-09-10 09:29:36
-
MORPHOLOGY OF DIAMOND SINGLE CRYSTALS GROWN IN THE Fe-Co-Mg-C SYSTEM
摘要： Diamond single crystals in a Fe-Co alloy with addition of 5 and 10 wt. % Mg by temperature gradient method were grown and their morphology was studied. For crystals obtained in the Fe-Co alloy with 5 wt. % Mg, the faces of octahedron, cube, rhomb-dodecahedron and tetragon-trioctahedron {311} were observed. When the magnesium content in the solvent-alloy increase up to 10 wt. % under the same growth conditions the tetragon-trioctahedron {311} faces on diamond crystals were absent. The topography of diamond crystals faces grown in different systems indicates that octahedron and cube are active growth forms with their growth pyramids, and rhomb-dodecahedron and tetragon-trioctahedron {311} are forms of passive growth.
关键词： A1.Crystal morphology,B1. Diamond,A2. Single crystal growth,A2. Growth from high temperature solutions
更新于2025-09-10 09:29:36
-
The new ordered double perovskite SrLaCuIrO6
摘要： The new fully rock-salt ordered Ir5+ double perovskite SrLaCuIrO6 was synthesized, and its structural, magnetic and electronic properties were investigated. The compound crystallizes tetragonally (space group I4/m). The Cu2+ cation leads to strong Jahn-Teller distortion of the CuO6 octahedra. The compound shows semiconducting behavior with an estimated band gap of approximately 0.2 eV. At around 10 K a magnetic transition is observed.
关键词： D. Magnetic properties,E. High-temperature synthesis,A. Double perovskite,D. Jahn-Teller distortion
更新于2025-09-10 09:29:36
-
Synthesis of Y2BaCuO5 nano-whiskers by a solution blow spinning technique and their successful introduction into single-grain, YBCO bulk superconductors
摘要： The ability of single grain Y-Ba-Cu-O (YBCO) bulk superconductors to trap large magnetic fields is due generally to the presence of embedded, non-superconducting Y2BaCuO5 (Y-211) phase particles, in optimum amount, in the superconducting YBa2Cu3O7-δ (Y-123) phase matrix, which increases flux pinning and, hence, critical current density of the bulk material. The presence of smaller particles of Y-211 could be expected to improve further the superconducting properties of single grain, bulk YBCO samples, although the smallest Y-211 particles that have been engineered to date within the bulk microstructure are around 800 nm in size. It is extremely challenging to reduce the Y-211 particle size any further due to problems of particle agglomeration that originate, inevitably, from the effects of surface energy and reactivity at relatively high processing temperatures. In this work, we report a novel approach to the fabrication of Y-211 pinning centres in bulk YBCO superconductors in the form of nano-whiskers manufactured by a solution blow spinning technique. The Y-211 nano-whiskers, of which 62% were smaller than 500 nm, were added to the YBCO precursor powders to produce a single grain bulk sample by the buffer-aided top-seeded melt growth (BA-TSMG) processing technique. The resulting YBCO single grain, of diameter 20 mm, was able to trap a magnetic field of 0.63 T at 77 K with an associated critical current density of 3.9 X 104 A/cm2 in self-field. The results of this study demonstrate clearly that the use of Y-211 nano-whiskers is a promising route for enhancing flux pinning in bulk YBCO single-grains, which is potentially significant for the development of high field engineering applications.
关键词： Solution Blow Spinning,nano-Y2BaCuO5,nano-whiskers,Bulk YBCO,High temperature superconductor,Single-grain superconductor,YBa2Cu3O7-x
更新于2025-09-10 09:29:36
-
The Self-Reaction of <i>ortho</i> -Benzyne at High Temperatures Investigated by Infrared and Photoelectron Spectroscopy
摘要： Ortho-benzyne, a Kekulé-type biradical is considered to be a key intermediate in the formation of polycyclic aromatic hydrocarbons (PAH) and soot. In the present work we study the ortho-benzyne self-reactions in a hot micro-reactor and identify the high-temperature products by IR/UV spectroscopy and by photoion mass-selected threshold photoelectron spectroscopy (ms-TPES) in a free jet. Ms-TPES confirms formation of ortho-benzyne as generated from benzocyclobutendione, as well as benzene, biphenylene, diacetylene and acetylene, originating from the reaction o-C6H4 → HCC-CCH + C2H2 , and CH3. PAH molecules like naphthalene, 2-ethynylnaphthalene, fluorene, phenanthrene and triphenylene are identified based on their IR/UV spectra. By comparison with recent computations their formation starting from ortho-benzyne can be readily understood and supports the importance of the biradical addition (1,4-cycloaddition followed by fargmenation) pathway to PAH molecules, recently proposed by Comandini et al.
关键词： photoelectron spectroscopy,Ortho-benzyne,high-temperature reactions,IR/UV spectroscopy,biradical addition,polycyclic aromatic hydrocarbons,PAH,soot
更新于2025-09-10 09:29:36