Synthesis and luminescent properties of Lu3Ga5O12 : RE3+ (RE = Eu, Tb, and Pr) nanocrystalline phosphors via sol-gel process

Lu3Ga5O12:Eu3+, Lu3Ga5O12:Tb3+, and Lu3Ga5O12:Pr3+ phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence, and cathodoluminescence spectra were utilized to characterize the synthesized phosphors. The XRD results reveal that the sample begins to crystallize at 800 degrees C and fully crystallined pure Lu3Ga5O12 phase can be obtained at 1000 degrees C. The FESEM image indicates that the phosphor sample is composed of aggregated rice grainlike particles with sizes around 80-120 nm.

One-Step Synthesis and Luminescent Properties of Nanocrystalline YVO4:Eu3+ powders

In this paper, nanocrystalline YVO4:Eu3+ powders have been successfully synthesized via high-temperature solution-phase synthesis process. The nanocrystalline YVO4:Eu3+ particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UVNis absorption spectra and luminescence spectra, luminescence decay curve and Fourier transform infrared (FT-IR), X-ray photoelectron spectra (XPS) respectively. The as-prepared nanocrystalline YVO4:Eu3+ particles are well crystallized with ellipsoidal morphology.

Perovskite-Like Mixed Oxides (LaSrMn1-x Ni (x) O4+delta, 0 a parts per thousand currency sign x a parts per thousand currency sign 1) as Catalyst for Catalytic NO Decomposition: TPD and TPR Studies

Catalytic NO decomposition on LaSrMn1-x Ni (x) O4+delta (0 a parts per thousand currency sign x a parts per thousand currency sign 1) is investigated. The activity of NO decomposition increases dramatically after the substitution of Ni for Mn, but decreases when Mn is completely replaced by Ni (x = 1.0). The optimum value is at x = 0.8. These indicate that the catalytic performance of the samples is contributed by the synergistic effect of Mn and Ni. O-2-TPD and H-2-TPR experiments are carried out to explain the change of activity. The former indicates that only when oxygen vacancy is created, could the catalyst show enhanced activity for NO decomposition; the latter suggests that the best activity is obtained from catalyst with the most matched redox potentials (in this work, the biggest Delta T and Delta E values).

A method for quantitative analysis of nitrogen oxides and N2 by means of mass spectrometry with the assistance of a catalytic technique for the reduction of NO with CO or hydrocarbons

Mass spectrometry is not able to differentiate NOx and N2 from other interferences (e.g. CO and C2H4) in the deNOx reactions. In the present study, a quantitative method for analysis of NOx and N2 simultaneously in these reactions with an assisted converter operated at higher temperature under O2-rich condition, which eliminates the interferences, is developed. The NOx conversion from this method is comparable to the one from an Automotive Emission Analyser equipped with NOx electrochemical sensor. Two types of deNOx reactions are tested in terms of selectivity of N2 production. The application of this method is discussed.

Chemical bond characteristics, thermal expansion property and compressibility of AR(2)O(4) (A = Ca, Sr, Ba; R = rare earths)

Theoretical researches were performed on the CaFe2O4-type binary rare earth oxides AR(2)O(4) (A = Ca, Sr, Ba; R = rare earths) by using chemical bond theory of dielectric description. The chemical bond properties of these crystals were explored, and then the thermal expansion property and compressibility were studied. The theoretical values of linear thermal expansion coefficient (LTEC) and bulk modulus were presented. The calculations revealed that the LTECs and the bulk moduli do have linear relationship with the ionic radii of the rare earths. In the cases of Sc and Y, both the LTEC and bulk modulus values are larger than the lanthanide series. We attribute this to the difference in the electronic configuration between Sc (Y) and lanthanide series. For SrY2O4 and BaY2O4 crystals, the theoretical values of LTEC and bulk modulus agree well with experimental ones.

Tm3+ and/or Dy3+ doped LaOCl nanocrystalline phosphors for field emission displays

Blue, yellow and white light emissive LaOCl:Tm3+, LaOCl:Dy3+ and LaOCl: Tm3+, Dy3+ nanocrystalline phosphors were synthesized through the Pechini-type sol-gel process. X-Ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), photoluminescence (PL) and cathodoluminescence (CL) spectra were used to characterize the samples. Under UV radiation (229 nm) and low-voltage electron beam (0.5-5 kV) excitation, the Tm3+-doped LaOCl phosphor shows a very strong blue emission corresponding to the characteristic transitions of Tm3+ (D-1(2), (1)G(4) -> F-3(4), H-3(6)) with the strongest emission at 458 nm. The cathodoluminescent color of LaOCl:Tm3+ is blue to the naked eye with CIE coordinates of x = 0.1492, y = 0.0684. This phosphor has better CIE coordinates and higher emission intensity than the commercial product Y2SiO5:Ce3+.

Nanocrystalline LaOCl:Tb3+/Sm3+ as promising phosphors for full-color field-emission displays

Nanocrystalline LaOCl:Tb3+/Sm3+ phosphors were synthesized by a Pechini-type sol-gel process. Under UV and electron-beam excitation, LaOCl:Tb3+/Sm3+ show the characteristic emission of Tb3+ (D-5(3,4) -> F-7(6), ... (2)) and Sm3+ ((4)G(5/2) -> H-6(5/2),(7/2),(9/2)), respectively. In particular, the cathodoluminescence (CL) color of LaOCl:Tb3+ can be tuned from blue to green by changing Tb3+-doped concentration, and their CL intensities (brightness) are higher than those of commercial products Y2SiO5:Ce3+ and ZnO:Zn, respectively. White CL can be realized by codoping with Tb3+ and Sm3+ in a single-phase LaOCl host. The obtained white light is very close to the standard white light. These phosphors are promising for application in field-emission displays.

Synthesis and Luminescent Properties of LaAlO3:RE3+ (RE = Tm, Tb) Nanocrystalline Phosphors via a Sol-Gel Process

LaAlO3:Tm3+ and LaAlO3:Tb3+ phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence, and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphors. The XRD results reveal that the fully crystalline pure LaAlO3 Phase can be obtained at 800 degrees C. The FE-SEM image indicates that the phosphor samples are composed of aggregated spherical particles with sizes ranging from 40 to 80 nm. Under the excitation of ultraviolet light (230 nm) and low-voltage electron beams (1-3 kV), the LaAlO3:Tm3+ and LaAlO3:Tb3+ phosphors show the characteristic emissions of Tb3+ (D-1(2)-> H-3(6,4),F-3(4) transitions) and Tm3+ (D-5(3,4)-> F-7(6,5,4,3) transitions) respectively. The CL of the LaAlO3:Tm3+ phosphors have high color purity and comparable intensity to the Y2SiO5:Ce3+ commercial product, and the CL colors of Tb3+-doped LaAlO3 phosphors can be tuned from blue to green by changing the doping concentration of Tb3+ to some extent.

Tunable Photoluminescence and Cathodoluminescence Properties of Eu3+-Doped LaInO3 Nanocrystalline Phosphors

LaInO3:Eu3+ phosphors were prepared by a Pechini sol-gel process. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), diffuse reflectance, photoluminescence, cathodoluminescence spectra, as well as lifetimes were utilized to characterize the synthesized phosphors. XRD results reveal that the sample begins to crystallize at 600 degrees C and pure LaInO3 phase can be obtained at 800 degrees C. The crystallinity increases upon raising the annealing temperature. The FE-SEM images indicate that LaInO3:Eu3+ phosphors are composed of fine and spherical grains around 40-80 nm in size. Under the excitation of UV light and low-voltage electron-beams, LaInO3:Eu3+ phosphors show the characteristic emissions of the Eu3+ (D-5(J)-F-7(J) J,J(')=0,1,2,3 transitions). The luminescence colors can be tuned from yellowish warm white to red by changing the doping concentration of Eu3+ to some extent. The corresponding luminescence mechanisms have been proposed.

Synthesis and luminescent properties of LaInO3: RE3+ (RE = Sm, Pr and Tb) nanocrystalline phosphors for field emission displays

LaInO3: Sm3+, LaInO3: Pr3+ and LaInO3: Tb3+ phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction, field emission scanning electron microscopy, photoluminescence, and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphors. XRD results reveal that the pure LaInO3 phase can also be obtained at 700 degrees C. FE-SEM images indicate that the LaInO3: Sm3+, LaInO3: Pr3+ and LaInO3: Tb3+ phosphors are composed of aggregated spherical particles with sizes around 80-120 nm. Under the excitation of ultraviolet light and low voltage electron beams (1-5 kV), the LaInO3: Sm3+, LaInO3: Pr3+ and LaInO3: Tb3+ phosphors show the characteristic emissions of Sm3+ ((4)G(5/2)-H-6(5/2,7/2,9/2) transitions, yellow), Pr3+ (P-3(0)-H-3(4), P-3(1)-H-3(5), D-1(2)-H-3(4) and P-3(0)-F-3(2) transitions, blue-green) and Tb3+ (D-5(4)-F-7(6.5,4.3) transitions, green) respectively. The corresponding luminescence mechanisms are discussed. These phosphors have potential applications in field emission displays.

Phase transformation and photoluminescence properties of nanocrystalline ZrO2 powders prepared via the Pechini-type sol-gel process

Nanocrystalline ZrO2 fine powders were prepared via the Pechini-type sol-gel process followed by annealing from 500 to 1000 degrees C. The obtained ZrO2 samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR), and photoluminescence spectra (PL), respectively. The phase transition process from tetragonal (T) to monoclinic (M) was observed for the nanocrystalline ZrO2 powders in the annealing process, accompanied by the change of their photoluminescence properties. The 500 degrees C annealed ZrO2, powder with tetragonal structure shows an intense whitish blue emission (lambda(max) = 425 nm) with a wide range of excitation (230-400 nm). This emission decreased in intensity after being annealed at 600 degrees C (T + M-ZrO2) and disappeared at 700 (T + M-ZrO2), 800 (T + M-ZrO2), and 900 degrees C (M-ZrO2). After further annealing at 1000 degrees C (M-ZrO2), a strong blue-green emission appeared again (lambda(max) = 470 nm).

PIFA-Mediated Oxidative Cyclization of 1-Carbamoyl-1-oximylcycloalkanes: Synthesis of Spiro-Fused Pyrazolin-5-one N-Oxides

convenient and efficient synthesis of spiro-fused pyrazolin-5-one N-oxides starting from readily available 1-carbamoyl-1-oximylcycloalkanes is developed. This general protocol features a novel and facile way for access to the five-membered azaheterocycles by formation of a new N-N single bond. The key cyclization step utilizes the formation of an N-oxonitrenium intermediate, mediated by the hypervalent iodine reagent PIFA, and its subsequent intramolecular trapping by the amide moiety under rather mild experimental conditions.

Nanocrystalline LaAlO3:Sm3+ as a Promising Yellow Phosphor for Field Emission Displays

Nanocyrstalline LaAlO3:Sm3+ phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), photoluminescence, and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphors. XRD results reveal that the sample begins to crystallize at 600 degrees C, and pure LaAlO3 phase can be obtained at 700 degrees C. FE-SEM images indicate that the Sm3+-doped LaAlO3 phosphors are composed of aggregated spherical particles with sizes ranging from 40 to 80 nm. Under the excitation of UV light (245 nm) and low-voltage electron beams (1-3 kV), the Sm3+-doped LaAlO3 phosphors show the characteristic emissions of the Sm3+ ((4)G(5/2)-H-6(5/2), H-6(7/2), H-6(9/2) transitions) with a yellow color. The CL intensity (brightness) of the Sm3+-doped LaAlO3 phosphor is higher than that of the commercial product [Zn(Cd)S:Ag+] (yellow) to some extent.

Nanocrystalline LaGaO3 : Tm3+ as an efficient blue phosphor for field emission displays with high color purity

Nanocrystalline Tm3+-doped LaGaO3 phosphors were prepared through a Pechini-type sol-gel process [M. P. Pechini, U.S. Patent No. 3,330,697 (11 July 1967)]. X-ray diffraction, field emission scanning electron microscopy, photoluminescence, and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphors. Under the excitation of ultraviolet light and low voltage electron beams (0.5-3 kV), the Tm3+-doped LaGaO3 phosphors show the characteristic emissions from the LaGaO3 host lattice and the Tm3+ (D-1(2), (1)G(4)-F-3(4), and H-3(6) transitions), respectively. The blue CL of the Tm3+-doped LaGaO3 phosphors, with a dominant wavelength of 458 nm, had better Commission International I'Eclairage chromaticity coordinates (0.1552, 0.0630) and higher emission intensity than the commercial product (Y2SiO5:Ce3+).

Tunable luminescence properties of Tb3+-doped LaGaO3 nanocrystalline phosphors

Nanocyrstalline Tb3+-doped LaGaO3 phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction, field-emission scanning electron microscopy (FESEM), photoluminescence, cathodoluminescence spectra, and lifetimes were utilized to characterize the synthesized phosphors. XRD results reveal that the sample begins to crystallize at 900 degrees C and pure LaGaO3 phase can be obtained at 1000 degrees C. FESEM images indicate that the Tb3+-doped LaGaO3 phosphors are composed of aggregated spherical particles with sizes ranging from 40 to 80 nm. Under the excitation of ultraviolet light and low-voltage electron beams (0.5-3 kV), the Tb3+-doped LaGaO3 phosphors show the characteristic emissions from the LaGaO3 host lattice and the Tb3+ (D-5(3,4)-F-7(6,5,4,3) transitions). The emission colors of Tb3+-doped LaGaO3 phosphors can be tuned from blue to green by changing the excitation wavelength of ultraviolet light and the doping concentration of Tb3+ to some extent. Relevant luminescence mechanisms are discussed.