In this paper, Ce-doped ZnO gas sensors with different Ce/Zn ratios have been fabricated by a facile hydrothermal process, starting from zinc acetate dihydrate, cerium(III) nitrate hexahydrate and PEG. The microstructure, morphologies and components of pure ZnO and Ce-doped ZnO are characterized by X-ray diffraction, scanning electron microscope and energy dispersive spectrometer, respectively. The sensitivities to testing gases are investigated through the static testing system. Compared with pure ZnO, Ce-doped ZnO sensors showed relatively higher sensitivity and faster response/recovery time. Among them, 3 at.% Ce-doped ZnO sensor exhibited a maximum sensitivity of 560 (Ra/Rg) for 300 ppm of 1,2-propanediol at the optimum operating temperature of 260 °C and the response and recovery time is 4 s and 16 s, respectively. Finally, the gas-sensing mechanism of ZnO sensors is discussed.

Ce3+ doped aluminosilicate phosphors (Ca2−xAlMg0.5Si1.5O7:xCe3+, x = 0.015–0.075) for white NUV w-LEDs were synthesized by a solid-state reaction method at 1250 °C. The as-prepared samples were characterized by XRD and fluorescence spectrophotometry; the obtained XRD results show that the target phase was synthesized and doping with Ce3+ did not result in an impurity phase. The as-prepared phosphors exhibit a strong blue-violet emission under the near-ultraviolet radiation excitation. Corresponding fitting results show the emission spectra contain two distinct single bands, which come from the transition of 2D3/2 → 2F7/2 and 2F5/2 of the Ce3+ ion. The colorimetric coordinates of the sample with x = 0.03 are (0.1574, 0.0359), located in the blue-violet region. In addition, the sample exhibits high external quantum efficiency (EQE = 37.3%) and excellent thermal stability (T50 = 230 °C). We obtained bright blue-violet light by pumping the sample with NUV light (λ ≈ 365 nm), which suggests that this material has the potential for application as a NUV converting blue-violet phosphor for the NUV w-LEDs.

•Single phase of Ba2Mg(PO4)2:Eu2+, Mn2+ co-doped phosphor was synthesized by a co-precipitation method.•The particles prepared by co-precipitation method have smaller size in diameter.•These phosphors show emission centered at 456 nm and 575 nm under near-UV excitation.•Transfer energy process from Eu2+ to Mn2+ has been investigated.The Ba2Mg(PO4)2:Eu2+, Mn2+ phosphor is synthesized by a co-precipitation method. Crystal phase, morphology, excitation and emission spectra of sample phosphors are analyzed by XRD, SEM and FL, respectively. The results indicate particles synthesized by a co-precipitation method have a smaller size in diameter than that synthesized by conventional solid-state reaction method. Emission spectra of BMP:Eu2+, Mn2+ phosphor show a broad blue and a broad yellow emission bands with two peaks at about 456 nm and 575 nm under 380 nm excitation. An overlap between Eu2+ emission band and Mn2+ excitation band proves the existence of energy transfer from Eu2+ to Mn2+. Emitting color of the BMP:Eu2+, Mn2+ phosphor could be tuned by adjusting relative contents of Eu2+ and Mn2+ owing to energy transfer formula. Therefore, BMP:Eu2+, Mn2+ may be considered as a potential candidate for phosphor for near-UV white LED.

•Highly visible-light active TiO2 photocatalyst was prepared via a novel method.•This method has potential to prepare nanostructure materials and dope metal ions.•The absorbance spectra of TiO2 have been adjusted into visible region.•The particle size of TiO2 nanoparticles has been decreased via doping Co2+.•We deduce the nano size effect exists in our samples.Mixed phases Co2+-doped TiO2 nanoparticles have been prepared by a novel method combined with sol–gel and hydrothermal methods. The section of sol–gel method, sol, provides an unstable colloidal reaction system for the next reaction process. The hydrothermal method is to treat the above reaction system to prepare undoped and doped samples. The as-prepared samples have been characterized by XRD, SEM, TEM, HRTEM and UV–vis spectroscopy. The results show that the as-prepared samples contain three titania polymorphs: brookite, rutile and anatase phases. These titania polymorphs probably form polymorph-junctions that can extend the lifetime of photogenerated electron–hole pairs. The photocatalytic activity has been evaluated by the photocatalytic degradation of Rhodamine B in air under visible-light irradiation. The degradation results indicate that the photocatalytic activity of as-prepared samples is higher than that of Degussa P25, especially the doped sample. This is ascribed to the fact that the phases with smaller band gap can enhance visible-light photocatalytic activity, the polymorph-junctions effectively extend the photoelectron lifetime and the nano size effect and Co-doping induce the shift of the absorption edge into the visible-light region. Furthermore, the XRD, SEM, and TEM data indicate that Co2+-doping results in the decrease of particle size.

Sr1.995–1.5xGdxSiO4:0.005Eu2+ phosphor series with x=0–0.08 mol for near-ultraviolet white light-emitting diodes (NUV w-LEDs) were synthesized via solid-state reaction method. XRD profile pattern and refinement results demonstrated that doping Gd3+ ions resulted in the phase transformation (β-Sr2SiO4→α'-Sr2SiO4). The photoluminescence spectrum of the sample with x=0 mol displayed two emission peaks centered at 470 and 525 nm. The two-peak spectra became one-peak spectra with the Gd3+ concentration increasing. Actually, the fitting results demonstrated that the one-peak spectra were still composed of two single emission spectra. The photoluminescence intensity was improved and the CIE chromaticity coordinates were adjusted via doping Gd3+.Emission spectra of Sr1.995–1.5xGdxSiO4:0.005Eu2+ (x=0–0.08 mol) (a) and Gaussian fitting results (x=0–0.04 mol) (b)

High-performance ZnO–Bi2O3 varistors co-doped with a fixed amount of La2O3 and different amounts of Sm2O3 have been fabricated from nanosize zinc oxide powders by solid-state reaction. Phase composition, microstructure, and electrical properties were studied by x-ray diffractometry (XRD), scanning electron microscopy, and direct current electrical measurement. XRD analysis of the samples showed that a ZnO phase, a Bi2O3-rich phase, a spinel phase, and a pyrochlore-type phase were present; an Sm-rich phase was found in varistor ceramics containing large amounts of Sm2O3. The varistor ceramics had fine microstructures, and the corresponding grain size varied from 2.30 to 3.10 μm. Varistor ceramics doped with 0.1 mol% La2O3 and 0.5 mol% Sm2O3 then sintered at 1100°C for 2 h had good electrical properties (a breakdown field of 1130 V/mm, a nonlinear coefficient of 74, and a leakage current of 4.2 μA).

Samples of Cu-Te-Se alloys, previously aged or treated as a solid solution, were immersed in 3.5% (mass fraction) sodium chloride solution to investigate their corrosion resistance at room temperature by determining their corrosive weight loss. The morphologies of the precipitated phase and surface products following immersion were observed by scanning electron microscope. In addition, energy-dispersive spectroscopic analysis was used to determine the elemental constituents of precipitated phase and corroded surface of the alloy samples. The phase composition was measured by x-ray diffraction, and the electrochemical polarization behavior of the samples was determined using an electrochemical workstation. The experimental results revealed that the alloy samples appeared to corrode uniformly, which was accompanied by a small amount of localized corrosion. There was the possibility that localized corrosion could increase following aging treatment. The addition of a small amount of tellurium and selenium to the alloy appeared to retard oxygen adsorption on the copper in the alloy, which has ameliorated the alloy corrosion due to the similar physical and chemical properties of oxygen. In comparison to the solid solution state, the corrosion resistance of the alloy appeared to decline slightly following aging treatment.