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Synthesis and mechanoluminescent property of (Eu2+, Dy3+)-co-doped strontium aluminate phosphor by soft mechanochemistry-assisted solid-state method
摘要： (Eu2+, Dy3+)-co-doped strontium aluminate (SrAl2O4:Eu2+, Dy3+) powder as a mechanoluminescent (ML) phosphor was synthesized via soft mechanochemical pretreatment of precursor mixtures in a stirred media mill and subsequent calcination. Effect of soft mechanochemical pretreatment of precursors on the synthesis process as well as the photoluminescent (PL) and ML properties of SrAl2O4:Eu2+, Dy3+ phosphor was investigated. The precursor mixtures unground and ground at different time and the resultant phosphors were characterized by laser particle size analysis, X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, Fourier transfer infrared spectroscopy and optical property measurement. The results reveal that soft mechanochemical pretreatment of precursor mixture promotes the crystal growth, and reduces the subsequent calcination temperature. SrAl2O4:Eu2+, Dy3+ phosphor can be obtained via calcining at 1200 oC for precursor mixture ground at 60 min, but formed via calcining at 1400 oC for unground precursor mixture. The phosphor synthesized with precursor mixture ground at 60 min has the maximum PL and ML intensities due to the enhancement of Eu2+ and Dy3+ ions into the crystal lattice to form more electron traps. The measurements by a designed ML instrument indicate that the ML intensity increases with increasing impact stress, and decreases with multiple applications of the same impact stress on phosphor disks.
关键词： Phosphor,Soft mechanochemistry,(Eu2+, Dy3+)-co-doped strontium aluminate,Solid-state method,Mechanoluminescence
更新于2025-09-23 15:22:29
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Performance of dye-sensitized solar cell (DSSC) using carbon black-TiO2 composite as counter electrode subjected to different annealing temperatures
摘要： Carbon black-TiO2 composite counter electrode was synthesized via solid state method and subsequently annealed at different annealing temperatures (450–550 °C). The composite was investigated as a counter electrode, acting as an alternative to platinum in a dye-sensitized solar cell. The aim is to obtain a higher conversion efficiency of solar energy being converted into electricity. The synthesized sample was structurally characterized by X-ray diffraction and it was found that annealing temperature strongly enhanced the anatase structure of carbon black-TiO2. The surface morphology and grain size were examined by field emission scanning electron microscopy which showed the presence of mesoporous structure; this is very important for high quality dye and electrolyte distribution. Electrochemical studies of carbon black-TiO2 counter electrodes suggest that increasing the annealing temperature may lead to increased charge transfer resistance which could contribute to decreased catalytic activity. The photovoltaic properties of carbon black-TiO2 were observed to be strongly influenced by the annealing temperature; measurements taken at annealing temperature of 525 °C showed the best photovoltaic properties of JSC = 6.10 mA/cm2, VOC = 0.51 V, FF = 0.89 and η = 2.77%.
关键词： Carbon black-TiO2 composite,Solid state method,Counter electrode,Annealing temperature
更新于2025-09-23 15:21:01
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Processing and Study of Optical and Electrical Properties of (Mg, Al) Co-Doped ZnO Thin Films Prepared by RF Magnetron Sputtering for Photovoltaic Application
摘要： In this study, high transparent thin films were prepared by radio frequency (RF) magnetron sputtering from a conventional solid state target based on ZnO:MgO:Al2O3 (10:2 wt %) material. The films were deposited on glass and silicon substrates at the different working pressures of 0.21, 0.61, 0.83 and 1 Pa, 300 °C and 250 W of power. X-ray diffraction patterns (XRD), atomic force microscopy (AFM), UV-vis absorption and Hall effect measurements were used to evaluate the structural, optical, morphological and electrical properties of thin films as a function of the working pressure. The optical properties of the films, such as the refractive index, the extinction coefficient and the band gap energy were systematically studied. The optical band gap of thin films was estimated from the calculated absorption coefficient. That parameter, ranged from 3.921 to 3.655 eV, was hardly influenced by the working pressure. On the other hand, the lowest resistivity of 8.8 × 10?2 ? cm was achieved by the sample deposited at the lowest working pressure of 0.21 Pa. This film exhibited the best optoelectronic properties. All these data revealed that the prepared thin layers would offer a good capability to be used in photovoltaic applications.
关键词： working pressure,Al doped ZnO-MgO powder,RF magnetron sputtering,photovoltaic applications,thin films,solid-state method,optoelectronic properties
更新于2025-09-23 15:21:01
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Spectroscopic Characterization of Er,Yb:Y <sub/>2</sub> Ti <sub/>2</sub> O <sub/>7</sub> Nanoparticles for Forensic Applications
摘要： Fingerprint identification technology has been widely utilized in the forensic field, given that the fingerprint is unique for each person and each finger and does not vary with age. In general, the fingerprints at a crime scene are latent and difficult to collect if the fingers were not contaminated with coloured materials, such as blood, ink or pigment. Moreover, the fingerprints on a smooth plane or transparent glass are hard to be visualized with traditional methods. In recent years, luminescent lanthanide-based nano-powder has been explored as a potential aid in fingerprint detection. Lanthanide based nano-materials have been analyzed because of the optical properties arising from the intra 4f transitions and of their relatively low toxicity. In principle, the technique allows the detection of latent finger-marks on a broad range of surfaces, like porous, semi-porous, non-porous and aged finger-marks. For the successful application of up-conversion phosphors in latent finger-marks detection, a phosphor should have good emission efficiency, uniform particle morphology, a dusty nature and stability against the humid environment. Y2Ti2O7 (YTO) belongs to the pyrochlore class and possesses peculiar thermodynamic and dynamic magnetic properties and has drawn researchers’ attention also for its upconversion emission properties or for ion-detection. In this work, we report the successful preparation of novel and non-toxic powder based on highly luminescent Er3+ and Er3+/Yb3+ codoped YTO nano-phosphors for fingerprint detection through solid- state method. To this aim, crystal structure, luminescence properties, morphology, and optimal doping concentrations have been investigated. Furthermore, the energy transfer processes between Er3+ and Yb3+ ion have been studied as a function of the concentration of Er3+ ions. Moreover, we used the optimized doped and co-doped YTO phosphors to detect fingerprints on the surface of different objects among which we chose several items commonly used in daily life, such as glass and plastic, where fingerprints are often left. The results reveal that the co-doped phosphors can efficiently manifest latent fingerprints with high contrast and low background interference, holding important application in fingerprint identification.
关键词： Y2Ti2O7,luminescent lanthanide-based nano-powder,fingerprint identification,solid-state method,Yb3+,Er3+
更新于2025-09-11 14:15:04