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[en] Graphical abstract: The phosphor powders of Ba_2ZnMoO_6:Eu"3"+ were prepared by sol–gel method. The dependence of luminescence intensity on the Eu"3"+ concentration was investigated. - Highlights: • We synthesize Ba_2ZnMoO_6:Eu"3"+ phosphors by the sol–gel method. • The effect of temperature on the crystallinity and morphology is investigated. • The phosphor presents an intense CT band in near UV range (370–410 nm). • The concentration quenching mechanism is the exchange interaction. - Abstract: Double-perovskite Ba_2Zn_1_−_xMoO_6:xEu"3"+ (x = 0, 0.02, 0.04, 0.06, 0.08, 0.1) orange–red emitting phosphors were synthesized by using the sol–gel method. The crystalline structure and photoluminescence properties of the phosphors were investigated. The X-ray diffraction (XRD) patterns indicate that the structure of matrix Ba_2ZnMoO_6 is cubic double-perovskite with space group Fm-3m. The Ba_2ZnMoO_6:Eu"3"+ phosphors present an intense broad charge transfer (CT) band absorption in near UV range (370–410 nm), which attributes to the charge transfer state of MoO_6, and performs orange–red emission of Eu"3"+ ("5D_0 → "7F_1 transition) at around 596 nm. A low concentration quenching occurs in Ba_2ZnMoO_6:Eu"3"+ and the optimal doping concentration is about 6 mol%. The Ba_2ZnMoO_6:Eu"3"+ phosphors are considered to be a promising orange–red emitting phosphor for near ultraviolet GaN-based white light emitting diode
[en] Highlights: • We synthesize novel NaY(MoO4)2:Eu3+ phosphors by the microwave hydrothermal method. • We observe and explain the subtle effect of reacting temperature on crystallinity. • NaY(MoO4)2:Eu3+ has a potential application as a red emitting phosphor. - Abstract: The Eu3+-doped NaY(MoO4)2 phosphors with a scheelite structure were synthesized using the microwave assisted hydrothermal process without further sintering treatment. X-ray powder diffraction (XRD) analysis indicates that the as-prepared products keep the tetragonal structure of NaY(MoO4)2. Scanning electron microscopy (SEM) images show that with prolonging the reaction time the morphologies of NaY0.9(MoO4)2:0.1Eu3+ phosphors evolve from rice-like to cubic micro-structure. The photoluminescence (PL) spectra demonstrate that the phosphors emit strong red light centered at 615 nm corresponding to 5D0 → 7F2 transition of Eu3+ ion under 465 nm excitation, which is in good agreement with the emission wavelength from blue light-emitting diodes (LEDs)
[en] Eu3+ and Sm3+ activated double molybdates, KY1−xLnx(MoO4)2 (Ln=Sm3+, Eu3+), were synthesized by a convenient solid-state method. The photoluminescence properties, energy transfer and concentration quenching were investigated in the excitation and emission spectra. The results exhibit that with Sm3+ and Eu3+ ions co-doped into the host, the excitations around 394 nm and 465 nm become broader and their intensities are prominently enhanced compared to that of the single Eu3+ doped sample. The effective energy transfer from Sm3+ to Eu3+ is found to exist for Sm3+ and Eu3+ co-doped KY(MoO4)2 phosphors. Besides, with increasing Eu3+ doping concentration, the chromaticity coordinates of KY1−xLnx(MoO4)2 (Ln=Sm3+, Eu3+) approach to the NTSC standard values in a systematic way. The KY(MoO4)2:Sm3+, Eu3+ phosphors may be potentially used as red phosphors for white light-emitting diodes. - Highlights: • We synthesize KY(MoO4)2:Sm3+, Eu3+ phosphors by the solid-state reaction technique. • The concentration quenching and energy transfer from Sm3+ to Eu3+ are investigated. • KY(MoO4)2:Sm3+, Eu3+ phosphors may be potentially used as red phosphors for w-LEDs
[en] Sr3−xEuxMoO6 and Sr2.7Eu0.3Mo1−yWyO6 red phosphors were successfully synthesized by solid-state reaction method at 1260 °C for 6 h. The photoluminescence (PL) properties of Eu3+ in this phosphor material were investigated by analyzing the excitation and emission spectra and the effect of Eu3+ concentration. X-ray diffraction (XRD) patterns indicate the formation of Sr3MoO6:Eu3+ pure phase. The excitation and emission spectra demonstrate that 30 mol% Eu3+:Sr3MoO6 shows a broad charge-transfer (CT) band at around 365 nm and an intense red emission (616 nm, 5D0→7F2 transition), with Commission Internationale de I'Eclairage (CIE) chromaticity coordinates (0.619, 0.376). The substitution of Mo6+ with W6+ results in a considerable enhancement of luminescence intensity and improved red color purity. All the results imply that the studied phosphors may be a promising red component for the application in the white light emitting diodes. - Highlights: • We synthesize Sr3EuMoO6:Eu3+ phosphors by solid-state reaction technique. • The phosphors show a broad CT band at around 365 nm and an intense red emission. • The substitution of Mo6+ with W6+ leads to a considerable improvement of PL. • The obtained phosphors may be potentially used as red phosphors for w-LEDs
[en] Polyaniline/CoRE_xFe_2_−_xO_4 (RE=La, Ce, Y, x=0.05–0.25) nanocomposites were successfully synthesized by a novel coordination-oxidative polymerization-hydrothermal method, and doped by sulfosalicylic acid. The resultant nanocomposites were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM) and electromagnetic measurements. The composites mainly showed nanofibers with a diameter of ca. 70 nm and a length longer than 2 μm. The surface of composites was uniformly covered with numerous nanoparticles with an average size of ca. 10–20 nm. Microwave absorption properties of polyaniline/CoRE_xFe_2_−_xO_4 nanocomposites doped with La ion were found to be better than those doped with Ce and Y ions. For the polyaniline/CoLa_xFe_2_−_xO_4 nanocomposite, the optimal microwave absorption performance is at x=0.15, that is, the mass ratio of La in CoLa_xFe_2_−_xO_4 is 7.5%, with the conductivity of the composite about 0.833 S/cm. Furthermore, when the layer thickness is 2 mm, the maximum reflection loss achieves the maximum number of −42.65 dB at 15.91 GHz with a bandwidth of 6.14 GHz above −10 dB loss, suggesting that these nanocomposites are excellent in microwave absorbing capacity. - Graphical abstract: Scheme PAn/CoRE_xFe_2_−_xO_4 nanocomposites prepared via a novel coordination-oxidative polymerization-hydrothermal route. - Highlights: • An organic–inorganic hybrid―polyaniline/CoRE_xFe_2_−_xO_4 (RE=La, Ce, Y, x=0.05–0.25) nanocomposites was prepared via a novel coordination-oxidative polymerization-hydrothermal route. • The as-prepared polyaniline/CoRE_xFe_2_−_xO_4 nanocomposites exhibit excellent microwave absorbing performance compared with the composites prepared by using conventional method. • The novel method reported in this work could be employed to prepare other conductive polymers/inorganic nanocomposites as well.
[en] Ca_9Y(VO_4)_7:Dy"3"+ phosphors were successfully synthesized by the solid-state reaction. X-ray diffraction, photoluminescence excitation and emission spectra were used to characterize the resulting samples. The phosphors under the excitation of charge transfer band exhibit blue emission (480 nm) and strong yellow emission (571 nm), corresponding to the "4F_9_/_2→"6H_1_5_/_2 and "4F_9_/_2→"6H_1_3_/_2 transitions of Dy"3"+ ions, respectively. The cross relaxation processes and the exchange interaction between Dy"3"+ ions are identified as the mechanisms for the concentration quenching. The color coordinate analysis indicates that Ca_9Y(VO_4)_7:Dy"3"+ phosphors may have potential applications for white light emitting diodes. - Highlights: • Ca_9Y(VO_4)_7:Dy"3"+ phosphors were synthesized first by solid-state reaction technique. • The phosphors emit blue emission (480 nm) and strong yellow emission (571 nm). • The phosphors may be a good candidate phosphor applicable for near UV w-LEDs
[en] Eu3+-activated novel potassium gadolinium double vanadates K3Gd(VO4)2 phosphors have been synthesized via solid-state reaction. The crystal phase, surface morphology and photoluminescence properties of the phosphor were investigated. X-ray diffraction results demonstrate that K3Gd1−xEux(VO4)2 has the monoclinic structure with the space group of p21/m(11). The emission spectra suggest that K3Gd1−xEux(VO4)2 phosphors present an intense charge transfer band at 314 nm and a strong red emission of Eu3+ (5D0 → 7F2 transition) at 617 nm. The optimum doping concentration of Eu3+ ions in K3Gd1−xEux(VO4)2 phosphors is around 50 mol% and the major mechanism for concentration quenching is the exchange interaction. The emitting light color of the phosphors can be tunable by varying excitation wavelength and a warm white light is achieved by the excitation at 337 nm. The luminescence properties suggest that the present phosphors may have potential applications as red and white emitting materials for w-LEDs in solid state lighting. - Highlights: • Novel K3Gd(VO4)2:Eu3+ phosphors were synthesized via solid-state reaction. • The photoluminescent properties of the phosphors were investigated. • The phosphor can emit multicolor light with tuning of excitation wavelength. • A warm white light is achieved under the excitation at 337 nm.
[en] Objective: To explore the relationship between speechlessness and the occurrence of deafness. Method: Had questionnaires on 78 children with speechlessness, and practiced the auditory brainstem response threshold value test on these patients. Results: Among the investigated patients, there are 23 examples of congenital deafness, 15 nereditary deafness, 13 brain gypoplasia confirmed by CT testing, 3 with history of Bilirubin encephalopathy, 8 with history of suffocation, 2 with history of high fever and convulsion, 5 with apparent history of using medicines with toxic effects to the ear, and 9 with uncertain causes. In the auditory brainstem response test, there are 62 increasing examples, 124 ears, for the children with speechlessness caused by brain hypoplasia and psychological reasons, the results of ABR are mostly abnormal. Conclusion: The main reason for speechlessness is the deterioration of hearing. Meanwhile, if the response threshold value indicates that the symptom is severe and extremely severe, the audiphone shall be used as early as possible
[en] Taking China Modified Pressure Reactor 1000 MW nuclear electrical station (CPR1000) steam generator(SG) as an example, the origin for the difference between gap measured and real gap for the thermal expansion of SG upper horizontal support is analyzed, and the optimized schemes ware proposed to improve the shim structure and the procedure about gap measurement and adjustment. The results show that the scheme is an effective way to solve the difficulties met during gap measurement and adjustment. (authors)
[en] Online upgrade of electronics system is usually needed in big physics experiment. It becomes possible because of universal use of Field Programmable Gates Array (FPGA). This paper introduces a scheme that a serial Flash and a Complex Programmable Logic Device (CPLD) is used to configure FPGA by passively serial mode (PS). The goal is achieved that is the auto configuration after power reset and the remote online upgrade and the function switch of electronics system. The rationale, system frame and hardware circuit of the scheme is also given. (authors)