Papers by Author: O. Milošević

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Authors: Lydia Mančić, G. del Rosario, Z. Marinković, O. Milošević
Abstract: The yttrium-aluminium garnet phase (YAG) represents a suitable host material for solidstate lasers and is widely used for various display applications being doped with rare-earth ions. Introduction of Ce3+ ion as a luminescence centre transforms it from insulating to effective phosphor material capable of emitting radiation in the visible spectrum. In this work Ce3+ doped YAG powder was obtained via aerosol route using nitrate precursor solution. Well-crystallized targeted phase was obtained after additional thermal treatment. A combination of different analysis techniques (differential scanning calorimetry, X-ray powder diffraction, scanning electron microscopy with determination of image metrology, energy dispersive spectroscopy, transmission electron microscopy) is used to obtain detailed information about the structural and morphological powder properties. The effects of both processing parameters and post annealing treatment conditions are discussed from the viewpoint of establishing the best relationship between them and produced YAG:Ce3+ crystal structure.
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Authors: Lydia Mančić, S. Grgurić-Šipka, V.M. Djinović, Z. Marinković, T. Sabo, O. Milošević
Abstract: Pt/Ru-doped ZnO nanophase particles were synthesized using ultrasonic spray pyrolysis. Particles were obtained through decomposition of zinc nitrate and newly developed Pt(IV) and Ru(III) complexes. The particle morphology, phase composition and chemical structure were revealed in accordance to various analysis methods (XRD, DSC, SEM/EDS, TEM) and discussed in terms of precursor chemistry and process parameters. The shape of DSC curves, indicating two exothermic effects above 6000C in both ZnO:Ru and ZnO:Pt, gave an indication of irreversible structural changes and high reactivity of as-prepared powders. The hexagonal wurtzite-type ZnO phase was revealed in both powdered samples. Small content of an intermediate Zn5(NO3)2(OH)8·2H2O and cubic Zn2PtO4 phase were detected in the Pt-doped ZnO particles. Structural refinements, performed by Koalariet-XFit, suggest the composite internal particle structure composed of primary particles sized less than 100 nm. The estimated values for the unit cell parameters and Zn-O bond lengths imply noble metal ions incorporation into ZnO matrix interstitially, probably in octahedral interstitial environment. It has been shown that different particle growing morphologies (either spheroidally or pyramidally shaped) were influenced by the precursor chemistry, processing parameters and the presence of noble metal ions. Among the many parameters, attaining of the particle shape uniformity and homogeneous distribution of the noble metal cations in as-prepared particles are regarded as the most important factors for dominating microstructure evolution.
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Authors: B.A. Marinković, Z. Žakula, S. Đurić, N. Nikolić, O. Milošević, Momcilo M. Ristić
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Authors: Ljiljana Kandić, K. Marinković, Lydia Mančić, G. del Rosario, O. Milošević
Abstract: The objective of this work is to present the results of the comparative analysis of YAG:Ce3+ microstructural parameters obtained from x-ray powder diffraction (XRPD) data using Rietveld based Koalariet and Fullprof programs. YAG:Ce3+ powder is obtained via low temperature aerosol route at 3200C followed by post annealing treatment. The chosen technique of synthesis, i.e. ultrasonic spray pyrolysis, provides the generation of spherically shaped and submicronically sized particles having composite nanostructure. Since the targeting garnet phase represents a very promising host phosphor material being doped with rare-earth ions, the most important criteria determining its applicability in various optical devices is the uniform distribution of the luminescent center in the host lattice as well as the cubic YAG phase crystallinity. Comparison of the data obtained for the same samples by the above mentioned XRPD analyses gives us an insight into the validity of the refined parameters.
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