Papers by Keyword: Y₂O₃:Eu

Abstract: Due to the advancing development of new technologies and consumer goods the future demand for raw materials will rise significantly. The finite primary raw materials will not be able to meet the demand quickly enough or the prices for the extraction will rise enormously. In consequence, a recycling of process waste and end of life products will be in future an essential step in order to meet the demand. Y₂O₃:Eu fluorescent phosphor was identified as the main composition in phosphor waste fractions and was chemical leached and bioleached with A. ferrooxidans. A selective leaching towards Y in bioleaching batches was observed and already after four days 100 % could be leached. The bioleaching with the bacteria showed no significant differences in comparison to the abiotic control without microorganism. Initial Fe³⁺ in the medium was identified as the driving force and lower extraction efficiencies of the biotic batches were attributed to a biosorption process and to high pH-values. This work showed that the extraction of yttrium out of waste products with high Y₂O₃:Eu content by chemical leaching with Fe-addition under mild conditions offers a good perspective to support the material demand of Y in the future growing market. In comparison to bioleaching of other fluorescent phosphors and waste fractions leaching efficiencies up to 100% were achieved and it was identified that the microorganisms can positively influence the leaching effect. Furthermore, it became obvious that the leaching behavior of microorganisms was highly dependent on the sample material. As relevant parameters mainly the structural composition of the phosphor was identified.

Abstract: Luminescence film material plays a very important role in display technology. In this paper, electrochemical deposition of luminescent Y₂O₃:Eu or Y₂O₃:Tb thin films on transparent conducting optically ITO glass substrates by cathodes reduction of yttrium nitric was investigated. Y(OH)₃ deposits were obtained using a conventional three electrode cell that potential of work electrode was –1.2v vs. Ag/AgCl electrode for 400 s in a 0.1mol/L Y(NO)₃ with 4%(mol/mol) Eu(NO)₃ at 65°C.Then this glass was sintered for 2h at 500°C.The luminescence spectrum of the film prepared by this method was tested. Its luminescent spectrum is the same as that of powder which prepared by solid method. Its XRD confirmed the formation of Y₂O₃ and SEM revealed uniformity of film.

Abstract: We synthesized nano-sized Eu-doped Y2O3 (Y2O3:Eu) phosphor powder by an ion-exchange po-lymer/water/oil (W/O) emulsion method using carboxymethyl cellulose (CMC) as the ion-exchange polymer, in which the CMC-(Y, Eu) gel formed was calcined at 800°C in air to convert into Y2O3:Eu particles. The obtained phosphor powder consists of unagglomerated particles with sizes in the range of 30-80 nm and exhibits strong red emission at 612 nm. This CMC/W/O method for producing nano-sized oxide powder has significant advantages over conventional solid-phase and chemical solution-based methods because this method can provide unagglomerated nanoparticles of oxide phosphor without employing any mechanical pulverizing process for reducing the particles’ size into the nanometer range; mechanical grinding, such as ball milling, of phosphor powders has been well known to cause a significant degradation of their luminescent properties.

Abstract: Luminescent and non-luminescent nano materials are used today in a variety of lighting applications. One example is the thin layer of densely packed nano alumina between glass and phosphor in fluorescent lamps that serves to increase the efficiency, to improve the maintenance and to reduce the mercury consumption of the lamps. Further, non-luminescent nano materials may be used to form a thin conformal coating around phosphor particles that protects the phosphor particles and improves the efficiency and maintenance of fluorescent lamps. Luminescent nano materials have been the subject of extensive research in the last 15 years. For particle sizes below 20 nm, the optical properties of nano phosphors change, e.g. the exciton energy increases and perhaps even more important, scattering decreases. We have synthesized nano Y2O3:Eu of particle sizes down to 10 nm, derived its optical properties, and investigated its use in Hg-free fluorescent lamps based on the Xe-excimer discharge. The possibility of using nano phosphors, e.g. semiconducting nano phosphors as CdSe or rare-earth doped phosphors as LaPO4:RE in LEDs, will be discussed.