Fabrication and upconversion luminescence properties of Er:SrF2 transparent ceramics compared with Er:CaF2

SrF₂ transparent ceramic is a promising upconversion material due to the low phonon energy. The effect of different sintering temperatures on Er:SrF₂ transparent ceramics was investigated. The suitable sintering temperature for Er:SrF₂ transparent ceramics was 900 °C by hot-pressed sintering in this study. High quality of Er:SrF₂ transparent ceramics with different doping concentrations were obtained. The upconversion luminescence spectra and decay behavior were compared between Er:SrF₂ and Er:CaF₂ transparent ceramics with different Er³⁺ doping concentration. The green emission of 5 at.% Er:SrF₂ ceramic was much stronger than that of 5 at.% Er:CaF₂ ceramic, while the red emission of Er:SrF₂ ceramic was almost the same as that of Er:CaF₂ ceramic. The upconversion luminescence lifetime of Er:SrF₂ transparent ceramics was longer than that of Er:CaF₂.All the results indicated Er:SrF₂ transparent ceramics was a candidate for green fluorescent upconversion materials.     

Influence of metal ion concentration in the glycol mediated synthesis of Gd2O3:Eu nanophosphor

The solvothermal synthesis of highly luminescent and homogeneous Gd₂O₃:Eu³⁺ nanophosphor using diethylene glycol as medium, followed by controlled combustion with citric acid as fuel is reported. The influence of concentrations of carboxylic acid and metal cations on the structure, morphology and luminescence properties are investigated in detail. The microscopic investigations indicate the nanocrystalline nature and the strong influence of cation concentration on the size, shape and agglomeration of the particles. It is found that increase in concentration of metal cations lead to the reduction in agglomeration of nanophosphors. The large value of intensity parameter Ω_2, suggested that Eu³⁺ ions reside in a more asymmetric environment, resulted in intense emission due to ⁵D₀–⁷F₂ electric dipole transition. Emission decay analysis of the samples exhibited one exponential nature. The samples prepared under optimum conditions showed a quantum efficiency of 78.63% and a moderately high life time of 1.217 ms.     

Improving lifetime of phosphorescent organic light-emitting diodes by using a non-conjugated hybrid host

Three hybrid host materials, mCP-PhSiPh3, mCP-L-PhSiPh3, and tBu-mCP-L-PhSiPh3, have been synthesized and characterized for their thermal, morphological, electrochemical, fluorescence, phosphorescence, and electroluminescence properties. The flexible spacer in mCP-L-PhSiPh3 and tBu-mCP-L-PhSiPh3 makes them maintain high triplet energies at about 3.00 eV due to the interruption of π-conjugation. The introduction of the tert-butyl group at the electrochemically active C3 and C6 sites of the carbazole moiety greatly improves thermal and electrochemical stability of the host tBu-mCP-L-PhSiPh3. Blue and green phosphorescent organic light-emitting diodes (PhOLEDs) based on the non-conjugated hosts exhibit external quantum efficiencies at around 15 and 21%, respectively. Higher current densities in PhOLEDs hosted by mCP-PhSiPh3 produce current leakage, resulting in lower efficiencies, especially in green PhOLEDs. The green PhOLEDs using non-conjugated hosts show improved device lifetime in comparison with the mCP-PhSiPh3 based PhOLED because of enhanced morphological stability. The operational stability of the tBu-mCP-L-PhSiPh3 based device is further raised because of improved electrochemical stability by employing the tert-butyl group. Our results demonstrate that both the flexible linkage and the blocking of the electrochemically active sites are crucial measures to realize long-lived PhOLED devices.     

Lifetime determination of tetragonal zirconia under static loading using the Constant Stress Rate method

Subcritical crack growth is a phenomenon which limits service time of a ceramic material. It is especially prevalent for oxides, because this phenomenon is attributed to the activity of water at the crack tip of the material and can be caused even by water present as a humidity in the air (Salem and Jenkins, 2002; Michalske and Freiman, 1983). It is very important to determine its lifetime at the setting loads with high probabilities of survival. The Constant Stress Rate method gives results that are sufficient for lifetime predictions. Estimations are based on n parameter which results from the slope of the strength vs. stress rate dependence. Only a conversion from dynamic to static conditions has to be done (Wojteczko et al., 2016). The attempts were made at different stress rates on sintered samples with pre-existing flaws and in two environments − air and water. Tetragonal zirconia was the tested material. Biaxial loading method was used for strength measurements. Microstructural and fractographic observations were made using the scanning electron microscope.     

Power grid redundant path contribution in system on chip (SoC) robustness against electromigration

The miniaturisation of integrated circuits leads to reliability issues such as electromigration (EMG). This well-known phenomenon is checked at design level by CAD tools. The conventional EMG check methods are based on electrical parameters. However, the wire physical degradation depends also on the interconnection network structure. In order to improve the EMG check methodologies, we propose an accurate method based on failure mechanism and chip power grid configuration. Indeed, the power grid offers redundant paths in case of void in main power supply path. The principle of our method is to take into account the contribution of these redundant paths in power grid lifetime assessment. These effects are validated by silicon ageing tests on structures designed in 28 nm Full Depleted Silicon on Insulator (FDSOI). These accelerated tests results have confirmed the lifetime gain due to the redundancy. These results provide perspectives for the relaxation of wire current limits and improve the chip design toward EMG.     

Enhanced red emission in LiAl5O8:Fe phosphor by B doping

Fe³⁺, B³⁺ co-doping LiAl₅O₈ phosphor has been successfully synthesized by a solid-state reaction method assisted with wet chemical mixing route. Photoluminescence emission peak is observed at around 672 nm excited at both 290 nm ultraviolet and 565 nm green light. With introduction of a small amount of boric acid, the red emission intensity can be enhanced by 2.62 times under 290 nm excitation and 2.31 times under 565 nm excitation, respectively. It is believed that the substitution of B³⁺ ions for Al³⁺ sites decreases the symmetry of the luminescence center, intensifying the red emission.     

层析介质使用寿命缩小模型的建立和确认

在现代生物制药工艺路线中,层析是最常用的一种技术手段。层析技术所需要的层析介质是药品监管的重点项目之一,其中层析介质的使用寿命(使用次数)必须经研究确认,并经药品监管部门审核和批准。在缩小模型上进行前瞻性研究是被广泛接受的层析介质使用寿命的研究方法。本文就层析介质使用寿命缩小模型的建立和确认作一简要综述。     

Synthesis,structural and luminescence properties of near white light emitting Dy-doped Y2CaZnO5 nanophosphor for solid state lighting

Novel near white light emitting Y₂CaZnO₅ (YCZ) nanocrystalline powders doped with Dy³⁺ ions were synthesized via the citrate gel combustion method. The structure of the compound is found to be triclinic with a particle size in the range of 20–30 nm. Luminescence properties have been characterized using photoluminescence (PL), excitation spectra and decay time measurements. The PL spectra have shown a broad blue band due to ⁴F_9/2→⁶H_15/2 transition and sharp yellow band corresponding to ⁴F_9/2→⁶H_13/2 transition of Dy³⁺ ions. From the concentration dependent PL studies, the optimum concentration of Dy³⁺ ions in YCZ is found to be 1.0 mol%, where intense near white light emission was observed. The Dy³⁺:YCZ nanophosphor has shown relatively better white color properties than the reported Dy³⁺:Y₂O₃ nanophosphor. The yellow to blue intensity ratios, CIE chromaticity coordinates and correlated color temperature studies have shown the possibility of using this compound for white light emission.     

Mechanical and Thermal Properties of Poly(Phthalazinone Ether Sulfone)/Poly(Ether Sulfone) Blends

The mechanical and thermal properties of poly(phthalazinone ether sulfone) (PPES)/poly(aryl ether sulfone) (PES) blends prepared by melt-mixing were investigated by dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). The dynamic mechanical thermal analysis results show that the incorporated PES has a large influence on the heat stability of PPES. The DMTA results display that the blends with a single glass transition temperature, which increases with increasing PPES content, indicates that PPES and PES are completely miscible over the studied composition range. The thermodegradative behavior of PPES/PES blends was used to analyze their thermal stability. The Friedman technique was used to determine the kinetic parameters (i.e., the apparent activation energy and order of reaction of the degradation process). The results indicate that the presence of the PES component influences the thermal stability of the PPES. On the basis of the kinetic data derived from Friedman' approach, the lifetime estimates for pure PPES, pure PES, and the blends generated from the weight loss of 5% were constructed.