ABSTRACT
Thermally stable SrWO4:[Er3+]/[Yb3+] upconversion phosphors were synthesized. X-ray diffraction analysis indicated a crystalline inorganic phosphor material with a tetragonal structure having a clear peak in the (112) phase, which is the main peak. The upconversion phosphor was synthesized using a precursor prepared by co-precipitation and sintered at 800 °C. When the phosphor was excited by a 980 nm laser with a pumping power of 200 mW, a strong green light was emitted. As the concentration of Er3+ ions increased, it was observed that the emission intensity decreased due to concentration quenching. The changes in the intensity of luminescence according to the pumping power are due to a two-photon process. As the temperature increased, the green emission intensity of the up-conversion phosphor increased. This was thought to be a phenomenon caused by efficient energy transfer between Yb3+ and Er3+ ions by the SrWO4 host with negative thermal expansion. A composite was prepared by mixing phosphor powder and PDMS, that could be used for temperature sensing.
ABSTRACT
Crystalline BaMoO4:Dy3+ and BaMoO4:Sm3+ phosphors were synthesized by co-precipitation at room temperature. The main peak (112) phase and tetragonal structure were confirmed using X-ray diffraction analysis. The lattice constant and Raman signal on d (112) were changed by the rare earth doping. A strong absorption wavelength appeared in the UV region, and BaMoO4:Dy3+ excited with UV wavelength showed a yellow spectrum. BaMoO4:Sm3+ showed a reddish orange spectrum. BaMoO4:[Sm3+]/[Dy3+] was synthesized for use as a white light phosphor, and the change in the emission characteristics of yellow, white, and reddish orange could be observed depending on the doping concentration of Sm3+ ions. The synthesized phosphor powder and PDMS polymer were mixed to form a flexible composite, and when applied on a UV-LED chip, the same color as the powder was realized, suggesting its use as an LED color filter.
ABSTRACT
The precursor prepared by co-precipitation method was sintered at various temperatures to synthesize crystalline manganese tungstate (MnWO4). Sintered MnWO4 showed the best crystallinity at a sintering temperature of 800 °C. Rare earth ion (Dysprosium; Dy3+) was added when preparing the precursor to enhance the magnetic and luminescent properties of crystalline MnWO4 based on these sintering temperature conditions. As the amount of rare earth ions was changed, the magnetic and luminescent characteristics were enhanced; however, after 0.1 mol.%, the luminescent characteristics decreased due to the concentration quenching phenomenon. In addition, a composite was prepared by mixing MnWO4 powder, with enhanced magnetism and luminescence properties due to the addition of dysprosium, with epoxy. To one of the two prepared composites a magnetic field was applied to induce alignment of the MnWO4 particles. Aligned particles showed stronger luminescence than the composite sample prepared with unsorted particles. As a result of this, it was suggested that it can be used as phosphor and a photosensitizer by utilizing the magnetic and luminescent properties of the synthesized MnWO4 powder with the addition of rare earth ions.
ABSTRACT
Er3+ and Yb3+ co-doped LaVO4 phosphors were synthesized by the facile solid state reaction method. Er3+ ions concentrations were changed from 0.01 to 0.2 mol for the fixed Yb3+ ions concentration at 0.15 mol. The crystalline structures of the phosphors were investigated by X-ray diffraction (XRD). The composition of the phosphors were investigated by X-ray photoelectron spectroscopy (XPS) analysis. The photoluminescence emissions based on the blue emission near 466 nm and green emission near 553 nm were observed and the highest emission intensity occurred for the sample LaVO4:Yb0.15, Er0.20. The green and red up-conversion emissions were observed in Er3+, Yb3+ co-doped LaVO4 phosphors under the excitation of 980 nm laser diode. LaVO3:Yb3+, Er3+ phosphors could be utilized to produce green colored LEDs by excitation for infra-red LED.
ABSTRACT
A rare-earth metal ion (Eu3+) doped ZnO nanocomposites have been successfully synthesized by employing wet chemical procedure using multi-wall carbon nanotubes (MWCNT's) as removable template. The preparation was carried out by immersing empty and dried MWCNT's in a stoichiometric composition of zinc nitrate and europium nitrate solution followed by filtration and sintering. The synthesized Eu3+ doped ZnO nanocomposites were characterized by means of different characterization techniques namely XRD, SEM, EDS, FT-IR and Raman spectroscopy. The XRD profile of the Eu3+ doped ZnO nanocomposites indicated its hexagonal nature while the photoluminescent analysis reveals that the prepared nanocomposite exhibits a strong red emission peak at 619 nm due to 5D0 --> 7F2 forced electric dipole transition of Eu3+ ions. Such luminescent materials are expected to find potential applications in display devices.
Subject(s)
Europium/chemistry , Luminescent Measurements/methods , Metal Nanoparticles/chemistry , Metal Nanoparticles/ultrastructure , Zinc Oxide/chemistry , Materials Testing , Particle Size , Surface PropertiesABSTRACT
A novel phosphor namely CaLa2ZnO5 doped with Eu3+ ions were prepared by conventional solid state reaction method. We have studied and optimized various constraints like sintering temperature, sintering time and dopant concentration. XRD, SEM profiles have been studied to explore its structural properties. Luminescence properties of these phosphors have been characterized by means of their photoluminescence (PL) spectra. We have noticed that the emission intensity of CaLa2ZnO5:Eu3+ phosphors strongly depend on its sintering temperature and Eu3+ concentration. Moreover, their PL spectra reveals that CaLa2ZnO5:Eu3+ phosphors exhibits a strong luminescence of 5D(0)_7F(2) transition at 627 nm under the excitation of 468 nm, which correspond to the popular emission line from a GaN based blue light-emitting diode (LED) chip. The obtained results of the prepared Eu3+ doped phosphors are very much encouraging and they are potentially useful in the development of new solid-state lightning devices.
