41 documents found, page 1 of 5
Catalysis of ceria incorporated magnesium hydride: a follow up study
Pukazhselvan, D.; Çaha, Ihsan; Jakka, Suresh Kumar; Graça, Vanessa C.D.; Holz, Laura I.V.; Soares, M.J.; Kovalevsky, A.V; Deepak, Francis LeonardIn continuation with the results explored in our recent previous study (https://doi.org/10.1016/j.apsusc.2021.150062), the current work sheds more light regarding the active in situ catalytic species in ceria additive loaded hydrogen storage system, MgH2. For this study, two samples, MgH2+0.167CeO2 and MgH2+0.5CeO2 were processed through mechanical milling (5 h/200 rpm) and tests were conducted at various stage...
Thermal sensing in NIR to visible upconversion of Ho3+ and Yb3+ doped yttrium o...
Jakka, S.K.; Soares, M.J.; Graça, M.P.F.; Neves, A.J.; Nagajyothi, P.C.; K, PavaniRare-earth (RE) oxyfluorides compatible for RE doping make a path for efficient near-infrared (NIR) to visible upconversion (UC). This paper describes the efficient use of YOF:Ho3+/Yb3+ phosphor nanoparticles synthesised by the Pechini sol-gel method as thermal sensors using UC in the visible region. Material characterisations such as X-ray diffraction, Raman spectroscopy and scanning electron microscopy (SEM),...
Analogy of different optical temperature sensing techniques in LaNbO4:Er3+/Yb3+...
Pavani, K.; do Nascimento, J.P.C.; Jakka, S.K.; do Carmo, F.F.; Sales, A.J.M.; Soares, M.J.; Graça, M.P.F.; de Aquino, F.J.A.; Gouveia, D.X.Three of the possible approaches to optical temperature sensing of a thermographic phosphor were formally compared in upconversion (UC) of Er3+ and Yb3+ doped lanthanum orthoniobate (LNO) phosphor. The three approaches used in the study were namely fluorescence intensity ratio (FIR) of thermally coupled levels (TCL), Valley to Peak ratio (VPR) and the ratio of non-thermally coupled levels (NTCL), respectively. ...
Sharp photoluminescence of Pr3+ ions in yttrium oxyfluoride nanospheres: thermo...
Suresh Kumar, J.; Pavani, K.; Graça, M.P.F.; Soares, M.J.YOF:Pr nanoparticles prepared by Pechni sol-gel method were investigated for temperature sensing in this work. Structural investigation such as XRD, Raman, SEM and EDS were done. Photoluminescence experiments at ambient temperature for three different concentrations and with variation in temperature were performed for application in fluorescence intensity ratio (FIR) technique. The FIR of the thermally coupled ...
Ba-doped ZnO nanostructure: X-ray line analysis and optical properties in visib...
Zamiri, Reza; Chenari, Hossein Mahmoudi; Moafi, H.F.; Shabani, Mehdi; Salehizadeh, S.A.; Rebelo, Avito; Kumar, J. Suresh; Graça, M.P.F.; Soares, M.J.In this work, X-ray diffraction analysis and optical properties of pure and Ba-doped ZnO nanoparticles prepared by the precipitation method were investigated. X-ray analysis was employed to evaluate the micro structural parameters of ZnO nanoparticles in terms of crystallite sizes and lattice strain by the Williamson–Hall method. The average crystallite size of Ba-doped ZnO nanoparticles estimated by the Willia...
YSZ:Dy3+ single crystal white emitter
Soares, M.R.N.; Soares, M.J.; Fernandes, A.J.S.; Rino, L.; Costa, F.M.; Monteiro, T.Dysprosium doped yttria stabilized zirconia single crystals grown by the laser floating zone method crystallize in the tetragonal form as confirmed by Raman spectroscopy. In addition to the role of the dysprosium ion as stabilizer, the ion optical activation constitutes an opportunity to explore the zirconia-based material in the photonics area. The spectroscopic characteristics of the doped fibers were analyze...
Bright room-temperature green luminescence from YSZ:Tb3+
Soares, M.R.N.; Nico, C.; Rodrigues, J.; Peres, M.; Soares, M.J.; Fernandes, A.J.S.; Costa, F.M.; Monteiro, T.The room temperature spectroscopic properties of terbium doped zirconia fibres grown by Laser Floating Zone method are reported. The fibres were found to be stabilised in the tetragonal crystalline phase as measured by X-ray diffraction and Raman spectroscopy techniques. The doping with terbium ions was performed during the growth process and their incorporation on the wide band gap oxide host assumes an import...
Structural and optical properties of Er implanted AlN thin films: green and inf...
Soares, M.J.; Leitão, J.P.; Silva, M.I.N. da; González, J.C.; Matinaga, F.M.; Lorenz, K.; Alves, E.; Peres, M.; Monteiro, T.In this work erbium ions were implanted into AlN films grown on sapphire with fluence range: (0.5-2) × 1015 at/cm-2, ion energy range: 150-350 keV and tilt angle: 0°, 10°, 20°, 30°. The optical and structural properties of the films are studied by means of photoluminescence and Raman spectroscopy in combination with Rutherford backscattering/channeling (RBS/C) measurements. The photoluminescence spectra of the ...
Damage recovery and optical activity in europium implanted wide gap oxides
Alves, E.; Marques, C.; Franco, N.; Alves, L.C.; Peres, M.; Soares, M.J.; Monteiro, T.In this study we compare and discuss the defects and optical behaviour of sapphire and magnesium oxide single crystals implanted at room temperature with different fluences (1 × 1015-1 × 1016 cm -2) of europium ions. Rutherford backscattering channelling shows that for fluences above 5 × 1015 cm-2 the surface disorder level in the Al-sublattice reaches the random level. Implantation damage recovers fast for ann...
Synthesis and optical properties of a lithium niobiosilicate glass doped with e...
Graça, M.P.F.; Valente, M.A.; Silva, C.C.; Peres, M.; Cruz, A.; Soares, M.J.; Neves, A.J.; Monteiro, T.The sol–gel method was used to prepare a lithium niobiosilicate glass doped with europium ions, 91SiO2–4Li2O–4Nb2O5–1Eu2O3 (% mole). The dried gel was heat-treated between 500 °C and 750 °C and glass ceramics were obtained. X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman studies show that crystallization starts at temperatures above 600 °C. The LiNbO3 and EuNbO4 nanocrystals were found in ...