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).

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.

Synthesis and luminescence properties of nanocrystalline Gd2O3 : Eu3+ by combustion process

The nanocrystalline Gd2O3:Eu3+ powders with cubic phase were prepared by a combustion method in the presence of urea and glycol. The effects of the annealing temperature on the crystallization and luminescence properties were studied. The results of XRD show pure phase can be obtained, the average crystallite size could be calculated as 7, 8, 45, and 23 run for the precursor and samples annealed at 600, 700 and 800 degrees C, respectively, which coincided with the results from TEM images. The emission intensity, host absorption and charge transfer band intensity increased with increasing the temperature. The slightly broad emission peak at 610 nm for smaller particles can be observed. The ratio of host absorption to O-2-Eu3+ charge transfer band of smaller nanoparticles is much stronger compared with that for larger nanoparticles, furthermore, the luminescence lifetimes of nanoparticles increased with increasing particles size. The effects of doping concentration of Eu3+ on luminescence lifetimes and intensities were also discussed. The samples exhibited a higher quenching concentration of Eu3+, and luminescence lifetimes of nanoparticles are related to annealing temperature of samples and the doping concentration of Eu3+ ions.

Study of the mechanism of nanocrystalline Pb(Zr0.52Ti0.48)O-3 prepared by accelerated sol-gel process

Nanocrystalline Pb(Zr0.52Ti0.48)O-3 was prepared from lead acetate, zirconium oxynitrate and titanium tetra-n-butoxide by a sol-gel method. It is found that both the crystallization temperature of precursor PZT and PZT product size were increased with increase of V(C3H8O2)/V(H2O) ratio in solution used. At V(C3H8O2)/V(H2O) = 4.47 the gel was formed moderately quick, and the nanocrystalline PZT with uniform granularity and low crystallizing temperature could be obtained. The diameter of the final nanocrystalline was ranged 60similar to70 nm as measured by atomic force microscopy (AFM). The crystallizing temperature of the precursor PZT was 443degreesC and the crystallization reaction was completed at 500degreesC by DTA and TG. The sol-gel reaction process was monitored by FT-IR and XRD.

Synthesis, reactive mechanism and thermal stability of W1-xAlxC (x=0.33, 0.5, 0.75, 0.86) nanocrystalline

W1-xAlxC (x = 0.33, 0.50, 0.75, 0.86) solid solutions have been synthesized directly by ball-milling tungsten powder, aluminum powder and activated carbon. The structural development of W0.5Al0.5C phase with the milling times up to 160 h has been followed using X-ray diffraction. X-ray photoelectron spectra demonstrate that Al atom takes the place of W. High temperature annealing experiment reveals that Al is stable in hexagonal structure to 1873 K. Transmission electron microscopy image shows that the grain size of the prepared powders is about 5 nm.

Nanocrystalline La2Mo2O9 and its characterization

In this work, both the thermal expansion and electrical conductivity of nanocrystalline La2Mo2O9 were studied. The nanocrystalline powder of La2Mo2O9 was obtained by sol-gel method, and with the help of SHP (superhigh pressure) up to 4.5 x 10(4) atm at 700 degrees C for a short time, and the nanocrystalline powder was densified without obvious particle size growth. The electrical conductivity of nanocrystalline La2Mo2O9 was one order of magnitude lower than that of the microcrystalline sample at the same temperature. Owing to the phase transition, the microcrystalline La2MO2O9 has an abrupt increase of thermal expansion with a peak value of 48 x 10(-6) K-1 at 556 degrees C. For the nanocrystalline material, the peak value increases to 112 x 10(-6) K-1 at 520 degrees C. On the other hand, above 600 degrees C the significant growth of particle size of the nanocrystalline La2Mo2O9 was observed, accompanying by a tremendous increase of thermal expansion with a peak value of 1565 x 10(-6) K-1 at 620 degrees C. The electrical conductivity of La1.6Nd0.4Mo2O9 at 800 degrees C is 0.14 S center dot cm(-1) which is about one third higher than that of La2Mo2O9.

Preparation of nanocrystalline NiZnCu ferrite particles by sol-gel method and their magnetic properties

Polyvinyl alcohol (PVA) was first used as chelating agent and metal nitrates as precursor of ferrite in the fabrication of nanocrystalline Ni0.65Zn0.35Cu0.1Fe1.9O4 particles by the sol-gel method. The thermal decomposition process of dried gel was studied by thermogravimetry (TG), differential thermal analysis (DTA) and infrared spectra (IR). The structural and magnetic properties of resultant particles were investigated by X-ray diffraction (XRD), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and Mossbauer spectroscopy. The dependence of the decomposition of dried gel, the formation of spinel structured NiZnCu ferrite, the sizes of annealed particles, the saturation magnetization and coercivity of annealed particles on annealing temperature is presented.

Combustion. synthesis and luminescence properties of nanocrystalline monoclinic SrAl2O4 : Eu2+

Nanocrystals of SrAl2O4:Eu2+ have been prepared by combustion synthesis. The results of XRD indicated that the resulting SrAl2O4:Eu2+ nanocrystals have a reduced and distorted monoclinic lattice compared with bulk materials. Both the excitation and emission spectra of SrAl2O4:Eu2+ nanocrystals shifts to higher energies in contrast to the bulk materials. The band structure calculation is performed using first-principles full potential-linearized augmented plane wave method within density functional theory. The calculated results are in reasonable agreement with our experimental results.

Dy3+- and Eu3+-doped LaGaO3 nanocrystalline phosphors for field emission displays

Nanocyrstalline LaGaO3 and Dy3+- and Eu3+-doped LaGaO3 were prepared through a Pechini-type sol-gel process. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence, cathodoluminescence spectra, and lifetimes were utilized to characterize the samples. XRD reveals that the samples begin to crystallize at 900 degrees C and pure LaGaO3 phase can be obtained at 1000 degrees C. FE-SEM images indicate that the Dy3+- and Eu3+-doped LaGaO3 samples are both composed of aggregated spherical particles with sizes ranging from 40 to 80 nm. Under the excitation of ultraviolet light and low voltage electron beams (1-5 kV), the undoped LaGaO3 sample shows a strong blue emission peaking at 433 nm, and the Dy3+- and Eu3+-doped LaGaO3 samples show their characteristic emissions of Dy3+ (F-4(9/2)-H-6(15/2) and F-4(9/2)-H-6(13/2) transitions) and Eu3+ (D-5(0,1,2)-F-7(1,2,3,4) transitions), respectively. The relevant luminescence mechanisms are discussed.

Preparation and optical properties of trivalent europium-doped bulk and nanocrystalline SrY2O4

The nanocrystalline Sry(2)O(4):Eu3+ was prepared by a poly(vinyl alcohol) (PVA)+glycine-assist combustion method. The results of x-ray diffraction indicate that the resulting Sry(2)O(4):Eu3+ nanocrystals have much broader and less intense peaks compared with those in bulk material. The charge-transfer bands in Sry(2)O(4):Eu3+ nanocrystals shift to higher energies in contrast to those in bulk material. The spectral results revealed that in bulk SrY2O4: Eu3+ the Eu3+ ions occupied three nonequivalent sites, with one at the Sr site: one at the Y(1) site and another at the Y(2) site, while in nanocrystalline SrY2O4: Eu3+, the Eu3+ ions occupied only two nonequivalent sites; one at the Y(1) site and the other at the Y(2) site. Finally, by theoretical calculation and analysis, the analyzed results are in reasonable agreement with our experimental results.

Sol-gel growth of Gd2MoO6 : Eu3+ nanocrystalline layers on SiO2 spheres (SiO2@Gd2MoO6 : Eu3+) and their luminescent properties

SiO2@Gd2MoO6:EU3+ core-shell phosphors were prepared by the sol-gel process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDS), transmission electron microscopy ITEM), photoluminescence (PL) spectra as well as kinetic decays were used to characterize the resulting SiO2@Gd2MoO6:Eu3+ core-shell phosphors. The XRD results demonstrate that the Gd2MoO6:Eu3+ layers on the SiO2 spheres begin to crystallize after annealing at 600 degrees C and the crystallinity increases with raising the annealing temperature. The obtained core-shell phosphors have a near perfect spherical shape with narrow size distribution (average size ca. 600 nm), are not agglomerated, and have a smooth surface. The thickness of the Gd2MoO6:Eu3+ shells on the SiO2 cores could be easily tailored by varying the number of deposition cycles (50 nm for four deposition cycles). The Eu3+ shows a strong PL luminescence (dominated by D-5(0)-F-7(2) red emission at 613 nm) under the excitation of 307 nm UV light.