Eu Solid Solutions Research Articles

Effects of Gd3+-doping on the fabrication and performances of highly transparent (Lu,Gd)2O3:Eu solid-solution ceramics

By pre-treating and component design of the ceramic powders, cubic (Lu,Gd)2O3:Eu solid-solution ceramics with high optical quality were achieved by the solid-state reaction method combined with vacuum sintering. The effects of Gd3+ doping (x = 0.05–0.6) on powder characteristics, phase compositions, microstructures and optical performances of the (Lu0.95-xGdxEu0.05)2O3 ceramics were systematically investigated to obtain the optimum Gd3+ content. The results indicated that the incorporation of moderate amounts of Gd3+ (5–50 mol%) effectively promoted mass diffusion and grain growth during sintering. The 50 mol% Gd3+-doped Lu2O3:Eu transparent ceramic (using the powder calcined at 1200 °C) sintered at 1750 °C for 5 h exhibited the optimum transmittance of 77.0 % in the visible spectral region (∼1 mm in thickness), which was significantly higher than the reported transmittance of vacuum sintered (Lu,Gd)2O3:Eu ceramics (less than 65.0 %). Owing to the lower electronegativity of Gd3+ relative to Lu3+, the bandgap energies of the final ceramics decreased gradually with increasing Gd3+ substitution, and the redshift of the CTB centre was observed with more Gd3+ addition. Under CTB excitation, the incorporation of Gd3+ enhanced the red emission intensity and shortened the fluorescence lifetime.

Effects of chemical composition control of colquiriite-type neutron scintillator single crystals

In this study, charge compensation was performed by co-doping Na + ions at the Ca2+ sites of Ce-doped LiCaAlF6 single crystals to prevent the generation of cation vacancies owing to Ce3+-doping at the Ca2+ sites. Consequently, an improved radiation resistance and increased light yield under neutron irradiation was achieved. In contrast, the Al metal of the starting material used as a substitute for AlF3 significantly increased the effective segregation coefficient keff of the Eu2+ ions in Eu-doped LiCaAlF6 and Eu-doped LiSrAlF6 single crystals. The Al metal and EuF3 in the starting materials produced EuF2 via a chemical reaction, and the Eu2+ ions in EuF2 could be substituted at the Ca2+ and Sr2+ sites. In addition, the Ca/Sr ratio control of the Li(Ca,Sr)AlF6:Eu solid-solution scintillator single crystals improved the light yield through band-gap control, and the Li(Ca,Sr)AlF6:Eu single crystal with a 25% Sr concentration exhibited the highest light yield.

Рентгенолюминесценция нанопорошков SrF-=SUB=-2-=/SUB=-: Eu

Concentration series of single-phase SrF2:Eu solid solutions with a particle size of ≈50 nm were synthesized by precipitation from aqueous solutions. The bands of europium in the di- and trivalent states as well as a band of intrinsic exciton luminescence of strontium fluoride were identified in the X-ray luminescence spectra. The most intense luminescence band is the band of trivalent europium with a maximum at 585–590 nm which corresponding to the 5D0 →7F1 transition. The highest X-ray luminescence intensities upon excitation by an X-ray tube with silver and tungsten anodes are achieved for compositions containing about 15.0 mol.% and 7.5 mol.% europium, respectively.

Determining the Photophysical Parameters of NaGdF4:Eu Solid Solutions in Suspensions Using the Judd—Ofelt Theory

The lifetime of the excited state of new NaGdF4:Eu solid solutions in dimethyl sulfoxide suspensions is determined using the Judd-Ofelt theory. A comparative analysis of the experimental and theoretical values of the lifetime of the excited state of NaGdF4:Eu solid solutions has shown that the Judd—Ofelt model adequately describes the photophysical processes in the studied substances.

BN-coated Ca1−xSrxS:Eu solid-solution nanowires with tunable red light emission

We report on the controlled growth of novel BN-coated Ca1−xSrxS:Eu nanowires via a solid–liquid–solid process. The Ca1−xSrxS solid solution forms as one-dimensional nanowires and has been coated with homogeneous protective BN nanolayers. The structure and luminescence properties of this new nanocomposite have been systematically investigated. High-spatial-resolution cathodoluminescence investigations reveal that effective red color tuning has been achieved by tailoring the composition of the Ca1−xSrxS nanowires. Moreover, codoping of Ce3+ and Eu2+ in the CaS nanowire can induce energy transfer in the matrix and make it possible to obtain enhanced orange color in the nanowires. The BN-coated Ca1−xSrxS:Eu solid-solution nanowires are envisaged to be valuable red-emitting nanophosphors and useful in advanced nanodevices and white LEDs.

A bona fide two-dimensional percolation model: an insight into the optimum photoactivator concentration in La2/3-xEuxTa2O7 nanosheets

La–Eu solid solution nanosheets La2/3−xEuxTa2O7 have been synthesized, and their photoluminescence properties have been investigated. La2/3−xEuxTa2O7 nanosheets were prepared from layered perovskite compounds Li2La2/3−xEuxTa2O7 as the precursors by soft chemical exfoliation reactions. Both the precursors and the exfoliated nanosheets exhibit a decrease in intralayer lattice parameters as the Eu contents increase. However, there is a discontinuity in this trend between the nominal Eu content ranges x≤ 0.3 and x ≥ 0.4. This discontinuity is attributed to the difference in degree of TaO6 octahedra tilting for the La- and Eu-rich phases. La2/3−xEuxTa2O7 nanosheets exhibit red emission, characteristic of the f–f transitions in Eu3+ photoactivators. The photoluminescence emission can be obtained from both host and direct photoactivator excitation. However, photoluminescence emission through host excitation is much more dominant than that through direct photoactivator excitation, and this behavior is consistent with that of all the other rare-earth photoactivated nanosheets reported previously. The absolute photoluminescence quantum efficiency of the La2/3−xEuxTa2O7 nanosheets increases as the experimentally determined Eu contents increase up to x=0.45 and decrease above it. This result is in good agreement with the optimum photoactivator concentration expected from the percolation theory. These solid solution La2/3−xEuxTa2O7 nanosheets are excellent models for validating the theory of optimum photoactivator concentration in the truly two-dimensional photoactivator matrix.

Synthesis of ZrO2:Eu solid solutions using homogeneous precipitation methods

Synthesis of ZrO2:Eu solid solutions using homogeneous precipitation methods

Evaluation and preparation of Li 1+ x− yNb 1− x−3 yTi x+4 yO 3 solid solution with superstructure as new phosphor

New red phosphors have been investigated in this study with europium as an activator added to Li 1+ x− y Nb 1− x−3 y Ti x+4 y O 3 (LNT) solid solutions with an M Phase superstructure. The photo-luminescence intensity of LNT:Eu solid solutions was dependent on the levels of both the Eu doping and the TiO 2 content, and was superior to that of LiNbO 3:Eu. LNT:Eu solid solutions with 2.5 wt.% Eu 2O 3 showed the highest performance in this work, and maximum intensity was observed when the TiO 2 content of LNT:Eu solid solutions was 10 mol.%. Structural analysis by XRD and HREM showed that in these new phosphors the M Phase superstructure was affected by the doping, with the periodicity of the superstructure becoming wider and more random.

P‐27: Investigation of the Excitation Functions in the Y2O3: Eu‐Gd2O3: Eu Luminecent System for the Voltage of 300–1000V

AbstractDependence of luminous efficiency in the Y2O3: Eu‐Gd2O3: Eu solid solutions which are highly promising for application in FED was studied. Their volt‐luminance characteristics have been explained on the basis of the sensibilization effects of the Eu3+ emission with Gd3+ ions and by decrease of the penetration depth of the primary electrons into the phosphor. This allowed to determine a thickness of a “dead layer” and to show its dependence on the phosphor synthesis conditions.

P‐50: Morphology and Luminescence Property of Gd2−xYxO3:Li, Eu (0.0 × 0.8), Red‐Phosphor with High Efficiency at Low Voltages

AbstractThe single phased Gd2−xYxO3:Li, Eu solid‐solution was successfully prepared by a citrate method at 650. Such a temperature is much lower than the typical solid‐state reaction or spray pyrolysis temperature (> 1300). However, additional heat treatment up to 850 ∼ 900 was required to obtain the optimum optical properties. Photoluminescence (PL), cathodoluminescence (CL), and morphology of Gd2−xYxO3:Li, Eu system were compared as a function of x values. The PL and particularly CL emission intensities at low‐voltages (< 1 kV) of this solid‐solution were 50 ∼ 80 % higher than those of commercial red phosphor Y2O3:Eu in the range of 0.0 × 0.8. This phosphor material appears to be very promising for field emission display (FED) because the particle size and shape are easily controlled at low temperature (900) by the change of Y or Li contents without any significant loss of brightness.

Analyses of the oxygen potential of the solid solutions MyU1−yO2+x (M = M3+andM2+) by statistics of defects and defect complexes

The oxygen potential, Δ G ̄ O 2 , of the solid solutions M y 3 U 1− y O 2+ x and M y 2+ U 1− y O 2+ x was analysed by calculating the number of ways of arranging the cationic defects as a function of x . The intra-cation complex (M 3+ U 5+ ) was assumed to be formed in M y 3+ U 1− y O 2+ x , while the presence of two kinds of complexes, i.e. (M 2+ U 5+ ) and (M 2+ 2U 5+ ), was assumed in M y 2+ U 1− y O 2+ x with an average composition, (M 2+ αU 5+ ). According to the experimental results reported, the x values at which the steepest change in Δ G ̄ O 2 takes place seem to be in the range of x < 0 for M y 2+ U 1− y O 2+ x , which was seen to be well explained by the present model as x = −(1 − α /2) y with α < 2 by calculating the number of ways of the arrangement of the above complexes. The model also makes it possible to explain the fact that the x value for the steepest change of Δ G ̄ O 2 is zero for M y 3+ U 1− y O 2+ x . By introducing a factor β (0 < β < 1), which is multiplied to the logarithmic term in Δ S ̄ O 2 , the oxygen potentials of the exemplified La, Mg and Eu solid solutions were found to be represented satisfactorily by the respective theoretical curves in a wide range of the x values. Calculations revealed that nearly x -independent Δ H ̄ O 2 values, as expected, could be obtained by using β.