AGATHA MATOS MISSO
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Resumo IPEN-doc 24521 CaMgSi2O6:Eu2+ and Dy3+ co doped phosphors prepared by combining two chemical method2017 - YAMAGATA, C.; MISSO, A.M.; MELLO-CASTANHO, S.R.H.; BRITO, HERMI F.; RODRIGUES, LUCAS C.V.Silicate system of the CaO–MgO–SiO2 has attracted great interest due to its high weather resistance which is endorsed by the physical and chemical stability [1, 2]. This property makes it applicable as host for luminescent materials. CaMgSi2O6 (diopside), an important component of the mantle and subduction slabs has been studied by many researchers [3]. Eu2+ activated alkaline earth silicate phosphors have a long afterglow characteristic and blue to green emission by the near ultraviolet [4] stimulation. Glass ceramic of CaO–MgO–SiO2 system has potential application on the optical devices [5, 6], for example, Ca2MgSi2O7:Eu2+ [7] and CaMgSi2O6:Eu2+, Dy3+ [8]. Ca2MgSi2O7: Eu2+ is a promising phosphor material for white light emitting diode (LED) [5]. In this study, CaMgSi2O6:Eu2+ and Dy3+co-doped CaMgSi2O6:Eu2+ phosphors were synthesized using sol gel technique followed by a modified molten salt method and thermal treatment in a weak reducing atmosphere. Crystalline phase identification by XRD and the measurements of photoluminescence (PL) excitation were performed. The XRD results reveal that the synthesized phosphors are crystalline and assigned to the diopside structure. The PL results indicate the emission spectra of CaMgSi2O6:Eu2+ and Dy3+ co-doped CaMgSi2O6:Eu2+ phosphors have a broad band at 450nm attributed to electronic transition from the 4f6 5d1 state to the 4f7 state.Resumo IPEN-doc 19084 Synthesis of Lasub(9,33)Sisub(6)Osub(26) oxyapatite powders by new modified sol-gel route: application as electrolyte for SOFC2013 - YAMAGATA, CHIEKO; MISSO, AGATHA M.; PAIVA, MAYARA R.S.; CASTANHO, SONIA R.H. de M.Artigo IPEN-doc 18918 Influence of the precursor concentration on the characteristics of silica powder obtained from Nasub(2)SiOsub(3) by a facile low temperature synthesis process2012 - YAMAGATA, CHIEKO; ELIAS, DANIEL R.; PAIVA, MAYARA R.S.; MISSO, AGATHA M.; MELLO CASTANHO, SONIA R.H.Artigo IPEN-doc 19079 Facile preparation of apatite-type lanthanum silicate by a new water-based sol-gel process2013 - YAMAGATA, CHIEKO; ELIAS, DANIEL R.; PAIVA, MAYARA R.S.; MISSO, AGATHA M.; CASTANHO, SONIA R.H.M.In recent years, apatite-type lanthanum silicates ([Ln10x(XO4)6O3–1.5x] (X = Si or Ge)) have been studied for use in SOFC (solid oxide fuel cells), at low temperature (600–800 8C), due to its ionic conductivity which is higher than that of YSZ (Yttrium Stabilized Zirconia) electrolyte. For this reason they are very promising materials as solid electrolyte for SOFCs. Synthesis of functional nanoparticles is a challenge in the nanotechnology. In this work, apatite-type lanthanum silicate nanoparticles were synthesized by a water-based sol–gel process, i.e., sol–gel technique followed by chemical precipitation of lanthanum hydroxide on the gel of the silica. Na2SiO3 waste solution was used as silica source. Spherical aerogel silica was prepared by acid catalyzed reaction, followed by precipitation of lanthanum hydroxide to obtain the precursor of apatite-type lanthanum silicate. Powders of apatite-type lanthanum silicate achieved from the precursor were characterized by thermal analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM) and specific surface area measurements (BET). The apatite phase was formed at 900 8C.