- 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
-
[Nanostructure Science and Technology] Nanowire Electronics || Metal-Semiconductor Compound Contacts to Nanowire Transistors
摘要： Semiconductor nanowires [1–4] are promising building blocks for next-generation ultrascaled devices for electronic [5–7] and optoelectronic [8–10] applications. An important aspect for the development, maturity, and ef?ciency of these ultrascaled devices is the detailed understanding of and control over the phase transformation that accompanies the formation of their compound contacts for lithography-free self-aligned gate design [11, 12]. The term “compound” here refers to the formed phases that have ?xed stoichiometry between metal and semiconductor elements, to be distinguished from the broader “alloy” term for phases that may include nonstoichiometric or amorphous structure. This distinction is important because the formation of a low resistance, crystalline, and thermally stable compound contact is most preferred for realizing reliable functionality in ultrascaled semiconductor transistors. Usually, the phase of compound contact and its interfacial property with semiconductor nanowire (NW) can largely affect the band alignment and charge injection in NW channels. This demands the detailed studies of the metal-semiconductor solid-state reactions, including the formed compound phases, reaction kinetics, and their correlation to the device performances. In this book chapter, we provide a thorough discussion of these three topics.
关键词： metal-semiconductor solid-state reactions,compound contacts,reaction kinetics,phase transformation,Semiconductor nanowires,device performances
更新于2025-09-10 09:29:36
-
High-frequency absorption properties of gallium weakly doped barium hexaferrites
摘要： The BaFe12-xGaxO19 (x < 1.2) hexaferrites were synthesised by usual ceramics technology. The Bi2O3 additive in the amount of 3 wt% was applied. The features of crystal structure and unit cell parameters were re?ned using powder X-ray di?raction at 300 K. It is shown that with the substitution level increase the parameters of unit cell monotonically decrease. The magnetisation and susceptibility versus temperature and ?eld for these solid solutions were investigated by the vibration magnetometry method. The main magnetic concentration dependence is shown that with the substitution level the magnetic parameters increase monotonically decrease. The microwave properties of the samples including the external magnetic bias ?eld are also investigated at 300 K. It is shown that with the increase of Ga3+ concentration from x = 0.1 to x = 0.6 the frequency value of natural ferromagnetic resonance (NFR) decreases in the beginning, and at further increase in concentration up to x = 1.2 it increases again. With the increase in Ga3+ concentration, the line width of the NFR increases that indicates the increase of frequency range where there is an intensive absorption of electromagnetic radiation (EMR). At the same time, the peak amplitude of the resonant curve changes slightly. The frequency shift of NFR in the external magnetic bias ?eld takes place more intensively for the samples with small Ga3+ concentration. It is shown the prospects of use of the Ga-substituted barium hexagonal ferrite as the material e?ectively absorbing the high-frequency EMR.
关键词： crystal structure,doped hexaferrites,magnetic and absorption measurements,Solid-state reactions
更新于2025-09-09 09:28:46
-
Silicide phase formation by Mg deposition on amorphous Si. Ab initio calculations, growth process and thermal stability
摘要： Formation of magnesium silicides on amorphous silicon by deposition of Mg at room temperature is studied by electron energy loss spectroscopy, differential reflectance spectroscopy and high resolution transmission electron microscopy. Optimal crystal structures of Mg silicides under high pressure are found by ab initio DFT calculations. These structures are related to the particular minima of enthalpy. Dielectric functions are calculated for these structures. The transitions from the cubic phase c-Mg2Si to orthorhombic o-Mg2Si at 5.6 GPa and then from o-Mg2Si to hexagonal h-Mg2Si at 22.3 GPa are predicted using the USPEX code. The experimental spectra and the data obtained from the calculated dielectric functions are mutually consistent. Optical reflectance is suitable for monitoring the growth and transformations of the phases during experiments. During Mg deposition onto amorphous Si, the o-Mg2Si phase forms first, then the c-Mg2Si phase grows upon it. The observed sequence of phase formation is related with the compression stress arising in the depth of the Mg-Si mixture.
关键词： optical reflection spectroscopy,electron energy loss spectroscopy,solid state reactions,thin films,high resolution transmission electron spectroscopy,ab initio calculations
更新于2025-09-09 09:28:46
-
Room temperature multiferroic properties of Fe-doped nonstoichiometric SrTiO3 ceramics at both A and B sites
摘要： This letter reports the structural, dielectric, ferroelectric, and magnetic properties of Fe substituted nonstoichiometric STO ceramics. X-ray diffraction and Scanning electron microscope reveal the microstructure of the samples. The room temperature multiferroicity of the Fe-doped Ti-rich STO ceramics is successfully realized by M-H hysteresis loop, P-E hysteresis loop and magnetodielectric measurement. The origins of ferroelectricity may be related to the lattice distortions and antisite-like defects with net local dipoles. The ferromagnetism are mainly contributed by the competitions among the double exchange interactions, super-exchange interactions and the non-linear ferromagnetic exchange coupling. In addition, the ordered spin arrangement of the ferromagnetism is formed by the exchange interaction of Fe atom using first principle simulations.
关键词： D. Ferromagnetism,A. Perovskite,E. Solid-state reactions,D. Ferroelectricity
更新于2025-09-09 09:28:46