Effects of compositional phase transitions on luminescence of Sr 1− x Ca x TiO 3:Pr 3+ (original) (raw)
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Investigation of luminescent properties inherent to SrTiO3:Pr3+
Semiconductor Physics Quantum Electronics and Optoelectronics, 2011
The red-emitting SrTiO 3 :Pr 3+ ,Al luminophors that can be used for the white light emitting diodes (LEDs) were prepared using the sol-gel method. The starting materials were SrCl 2 , Ti (O-i-C 3 H 7) 4 , Al(NO 3) 3 •9H 2 O and PrCl 3. The reaction between them results in a mixture of compounds that transform into single-phase SrTiO 3 :Pr 3+ ,Al after annealing in air. Displacement of Ti out of the SrTiO 3 lattice caused by substitution with Al and formation of individual crystalline TiO 2 phase (rutile) were observed. PL spectra show the high-intense red peak (λ = 617 nm), the same high-intense peak with the full width at half maximum (FWHM) 20 nm was found in cathodoluminescence spectra. The increase of the aluminium concentration from 0 up to 15 mol.% leads to approximately twofold increase in the luminance. The latter increases from 180 up to 350 cd/m 2 at the anode voltage 10 kV and current density 30 μA/cm 2 .
Enhancement of the red emission in CaTiO3:Pr3+ by addition of rare earth oxides
Chemical Physics Letters, 2007
Enhancement of the 1 D 2-3 H 4 red emission of CaTiO 3 :Pr 3+ with addition of rare earth oxides Ln 2 O 3 (Ln = Lu, La, Gd) is reported. Ca 2+ and Ti 4+ in CaTiO 3 can be substituted by Ln 3+ ions as donors and acceptors, respectively. Ca 2+ and Ti 4+ vacancies, as quenching centers in the host, are effectively suppressed by the self-compensation, leading to the increase of lifetimes and then the emission efficiency of 1 D 2. The red fluorescence intensity for CaTiO 3 :Pr 3+ phosphor co-doped with 5 mol% Lu 2 O 3 is nearly 3 times greater than that of the Lu-free samples.
Improvement of the optical performances of Pr3+ in CaTiO3
Journal of Alloys and Compounds, 2001
Trivalent praseodymium-doped calcium titanates are red emitting phosphors upon UV photon excitation in the range 150-300 nm, with a luminescence appearing as a single peak centered at 613 nm. The intensity of this emission is investigated in different samples prepared either by a solid state or a sol-gel method. The study includes analyses of microstructure, sintering temperature, charge compensation and Pr concentration effects.
2018
Preparation, characterization and temperature-dependent photoluminescence in Ca0.90Sr0.10RuO3 compound A. Quiroza,b,∗, M. Abatal, E. Chavira, V. Garcia-Vazquez , E. Marinero, and M. Nishioka Facultad de Ingenier ı́a, Universidad Aut́ onoma del Carmen, Av. Central S/N Esq. Con Fracc. Mundo Maya, Ciudad del Carmen, Campeche, 24115 Mexico. Instituto de Investigaciones en Materiales, Universidad Nacional Aut ónoma de Ḿexico, Apartado Postal 70-360 Ciudad de M éxico, 04510 Mexico. Instituto de F́ısica Luis Rivera Terrazas, Benem ́ rita Universidad Aut́ onoma de Puebla, Apartado Postal J-48, Puebla, Pue., 72570 Mexico. Purdue University, Hovde Hall, 610 Purdue Mall, West Lafayette, IN 47907-2040 USA. Hitachi San Joś e Research Center, San Jos é California 3403, Yerba Buena Road, 95135 USA.
Optical spectroscopy of Ca3Sc2Si3O12, Ca3Y2Si3O12 and Ca3Lu2Si3O12 doped with Pr3+
Journal of Luminescence, 2010
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Synthesis and spectroscopic properties of CaTiO3 nanocrystals doped with Pr3+ ions
Journal of Alloys and Compounds, 2008
Ruthenium(II) diimine complexes with their extraordinary photophysical and photochemical properties have been a center of interest in the past four decades as such complexes characterized with strong absorbence in the visible domain due to the metal-to-ligand charge transfer "MLCT" as well as the long lifetimes for the triplet excited states that are resulted from the spin-orbit coupling. A wide range of ruthenium(II) diimine complexes are reported and their photophysical behaviours were characterized. Among the different possible ruthenium(II) diimine, homoleptic bis-diimine and tris-diimine ruthenium complexes extensively studied. They are obtainable by refluxing ruthenium(III) chloride hydrate or some other ruthenium(II) complexes with the right ratio of the ligand in alcohols or N,Ndimethylformamide (DMF) [1-5]. Synthesis of heteroleptic bis-diimine and tris-diimine ruthenium(II) complexes have also been reported, showing the possibility of adjusting the excitedstate properties by the presence of different substituents on the diimine ligands [6-14]. Recent research in the area proved that the quantum yields of the luminescence in this class of complexes are affected by the presence of the competing nonradiative decay originated from thermal activation to the triplet metal-centered (3 MC) excited states. The decay from the 3 MC excited states facilitates the ligands dissociation; resulting possibly in decomposition or ligand substitution.
Complex cluster TiO5·VO z and SrO11·VO z where VO z =VO X, VO • , VO •• vacancies were identified in disordered SrTiO3 powders prepared by the polymeric precursor method, based on experimental measurements by x-ray absorption near edge structure spectroscopy. The paramagnetic complex states of TiO5·VO • and SrO11·VO • with unpaired electrons were confirmed by electron paramagnetic resonance spectroscopy.The disordered powders showed strong photoluminescence at room temperature. Structural defects of disordered powders, in terms of band diagram, density of states, and electronic charges, were interpreted using high-level quantum mechanical calculations in the density functional framework. The four periodic models used here were consistent with the experimental data and explained the presence of photoluminescence.
Journal of Physics: Condensed Matter, 2006
Results of a powder x-ray diffraction study are presented to show that the socalled 'nearly cubic' phase region of Sr 1−x Ca x TiO 3 , in fact, corresponds to two different types of crystal structures. The 'nearly cubic' phase occurring in the composition range 0.35 < x < 0.41 is antiferroelectric in nature and its most plausible space group is Pbcm, while the crystal structure of the 'nearly cubic' phase for 0.41 x < 0.70 belongs to the space group Pbnm. This space group persists up to x = 1.0, even though the 'nearly cubic'-like features disappear for x 0.70. There are two other phase boundaries which occur around 0.05 < x < 0.06 and 0.35 < x < 0.36 and correspond to the change of structures with space groups Pm3m to I bmm and I bmm to Pbcm, respectively.
UV and Visible Luminescence of Pr3+ Doped Oxides: New Materials
MRS Proceedings, 2008
The garnet Ca3Sc2Si3O12 (CSSO) and the silico-carnotite Ca3Y2Si3O12 (CYSO) and Ca3Lu2Si3O12 (CLSO) materials, both undoped and doped with Pr3+, have been synthesized by solid state reaction at high temperature. The luminescence spectroscopy and the excited state dynamics of the materials have been studied upon VUV and X-ray excitation using synchrotron radiation. All doped samples have shown efficient 5d-4f emission upon direct VUV excitation of 5d levels, but only CSSO:Pr3+ shows luminescence upon interband VUV or X-ray excitation. The VUV excited emission spectra of CYSO:Pr3+ and CLSO:Pr3+ show features attributed to emission from two distinct sites accommodating the Pr3+ dopant. The decay kinetics of the Pr3+ 5d-4f emission in CSSO:Pr3+ upon VUV excitation across the conduction band are characterized by decay times in the range 25-28 ns with no significant rise after the excitation pulse. They appear to be faster upon X-ray irradiation than for VUV excitation. Weak afterglow comp...
Blue-green and red photoluminescence in CaTiO 3:Sm
Journal of Luminescence, 2007
Ca 0.95 Sm 0.05 TiO 3 (CT:Sm) powder was prepared by the polymeric precursor method (PPM). Orderdisorder at short and long range has been investigated by means of Raman spectroscopy, X-ray diffraction (XRD), and photoluminescence emission (PL) experimental techniques. The broad PL band and the Sm emission spectrum measured at room temperature indicate the increase of structural order with annealing temperature. The measured PL emission reveals that the PL intensity changes with the degree of disorder in the CT:Sm. The electronic structures were performed by the ab initio periodic method in the DFT level with the hybrid nonlocal B3LYP approximation. Theoretical results are analyzed in terms of DOS, charge densities, and Mulliken charges. Localized levels into the band gap of the CT:Sm material favor the creation of the electron-hole pair, supporting the observed room-temperature PL phenomenon.