Gd2O3 Content Research Articles

Facile Fabrication and Properties of Gd2O3:Eu3+, Y2O3:Eu3+ Nanophosphors and Gd2O3:Eu3+/Silica, Y2O3:Eu3+/Silica Nanocomposites

Gd2O3:Eu3+ and Y2O3:Eu3+ nanophosphors have been successfully fabricated by a combustion method at low temperature (350°C) in a short time (5 min) using natriethylenediaminetetraacetic acid (EDTA-Na2) as fuel. The structure, morphology and size of Gd2O3:Eu3+ and Y2O3:Eu3+ nanophosphors have been determined by x-ray diffraction and field emission scanning electron microscopy. Photoluminescence spectra indicated that the optimum Eu3+ ion concentrations with the strongest luminescence emission intensities are 5 mol.% for Y2O3:Eu3+ and 7 mol.% for Gd2O3:Eu3+. The nanocomposites of Gd2O3:Eu3+/silica and Y2O3:Eu3+/silica were fabricated by a sol–gel process with tetraethoxysilane (TEOS) as matrix material, and the nanocomposite compositions were analyzed by energy dispersion spectra. The strongest luminescence peaks from the 5D0–7F2 transition of the Eu3+ ion in Gd2O3:Eu3+ and Y2O3:Eu3+ nanophosphors are between 613 nm and 615 nm. The Gd2O3:Eu3+ and Y2O3:Eu3+ nanophosphors and their silica nanocomposites were studied to elucidate the influences of the Eu3+ concentration, host materials, annealing temperature, and weight ratio of TEOS and Gd2O3:Eu3+ or Y2O3:Eu3+.

Densification and microstructure of spark plasma sintered 7YSZ–Gd2O3 ceramic nano-composites

Spark plasma sintering (SPS) technique was used to densify 7 mol% yttria-stabilized zirconia (7YSZ) powder with Gd2O3-particles, at temperatures ranging between 1000 and 1200 °C. Fine dispersion of Gd2O3-particles into a full-densified matrix was achieved. Shrinkage and microstructure, as well as porosity were investigated. The fine Gd2O3-particles distributed into 7YSZ matrix have influence over the sintering consolidation and final microstructure. An increment in the spark plasma sintering temperature around 70 °C is detected when Gd2O3 particles are present. The thermal characterization was performed using the photothermal infrared radiometry technique. Both thermal diffusivity and thermal conductivity display a similar sigmoidal (Boltzmann type) behavior with the Gd2O3 concentration in the samples.

Large improvement on energy storage and charge-discharge properties of Gd2O3-doped BaO-K2O-Nb2O5-SiO2 glass-ceramic dielectrics

Potassium barium niobate-based glass ceramics doped with different proportion of Gd2O3 were fabricated by conventional melts and controllable crystallization. The influence of Gd2O3 content was further investigated on the phase compositional change, energy storage performance and charge-discharge properties of the optimized glass ceramics (crystallization temperature 900°C). The microstructure has been remarkably transformed through the addition of Gd2O3. On the basis of the results, the doping of 1.0% Gd2O3 achieved a remarkable improvement on the energy storage density that reached 12.14J/cm3 with a dielectric breakdown strength (BDS) of 1818kV/cm and dielectric constant of 83. The discharge efficiency of 80% and discharge time of 25ns were obtained in the glass ceramics with 1.0% Gd2O3, which illustrated the excellent charge-discharge properties of Gd2O3-doped glass ceramics.

Fabrication of new high temperature Gd2O3-ZrO2 insulation coatings on Ag tapes by sol-gel technique for magnet technology

Cost-effective and easy-to-apply materials are necessary for magnet technologies. This research covers a fabrication development of high temperature insulation coatings for magnet technologies. With this context, gel coatings were successfully deposited on Ag tapes using sol-gel technique by preparing transparent solutions from Gd- and Zr-based precursor materials, methanol and glacial acetic acid, and subsequently 0, 5, 8, and 12 mol% Gd2O3-ZrO2 coatings were heat treated at 300, 500, and 800 °C which respectively indicate drying, heat treatment, and annealing processes. Prior to coating process, Gd2O3 effect on thermal, structural and microstructural, and electrical properties were observed and extensively discussed in the present study. FTIR revealed that when increasing heat treatment temperature from 25 to 800 °C, the frequencies of O-H, C-H, and C=O bands decreased. According to XRD results, Gd2O3 additive has a propensity to generate tetragonal ZrO2 and help to stabilize it. It was also observed that the regular surface morphology generally forms when Gd2O3 content increase in ZrO2 from 0 to 12 mol%. The film thicknesses increased from 0.5 to 1.8 μm as a function of number of dipping. The porosities of the insulation coatings can be estimated to be in the range of 25 and 40 vol%. Besides, as insulative layers, Gd2O3 additive improved ZrO2 coatings. As a result, commercial Ag and AgMg sheathed Bi-2212 long length tapes can be insulated with pure ZrO2 and Gd2O3–ZrO2 coatings and then the coated tapes can be wound to fabricate an electromagnet.

Effect of particle size on gamma radiation shielding property of gadolinium oxide dispersed epoxy resin matrix composite

Epoxy resin matrix composites filled with dispersed micro and nano gadolinium oxide (Gd2O3) particles of different contents were fabricated in this study. The γ radiation shielding and mechanical properties of these micro and nano composites were evaluated by measuring mass attenuation coefficients at photon energies from 31 keV to 356 keV and flexural performances. Adding Gd2O3 obviously increases mass attenuation coefficients of composites, and the enhancement is stronger at low photon energy because of dominating photoelectric effect and k-edge of element gadolinium. Effect of Gd2O3 particle size on shielding property of composite was also discussed. The results show that nano-Gd2O3 composites have better ability to shield X and γ ray than micro-Gd2O3 composites, and an enhanced effect of ~28% is obtained with Gd2O3 content of around 5 wt.% at 59.5 keV. The reason is attributed to higher probability of interaction between γ-ray and nano particles. Especially, this effect is prominent in low particle concentration. For flexural property, nano-Gd2O3/epoxy composite show equivalent flexural strength and up to15% higher flexural modulus compared with micro-Gd2O3/epoxy composite. Based on these experimental results, nano-Gd2O3 reinforced epoxy composite is believed to be a promising novel radiation shielding material.

Development of gadolinium calcium phosphate oxyfluoride glass for radiation shielding materials

ABSTRACTIn this work, Gd2O3 based glasses with compositions 10CaF2:xGd2O3:(90-x)P2O5 (where x = 5, 10, 15 and 20 mol%) have been prepared by using melt-quenching method and investigated their physical, optical and gamma-ray shielding properties. The total mass attenuation coefficients increased with increasing Gd2O3 concentration and decreased with increasing of photon energies. The effective atomic numbers and the effective electron densities are in the same trend with the total mass attenuation coefficients. The Half-value layers (HVL) at 662 keV were found to decrease with increasing Gd2O3 concentration. All studied glasses have the HVL values lower than some standard shielding, ordinary concretes and commercial window, indicating the potential of the prepared glasses as a radiation shielding material.

Immobilization of gadolinium in iron borophosphate glasses and iron borophosphate based glass-ceramics: Implications for the immobilization of plutonium(Ⅲ)

Immobilization of gadolinium (Gd), a nonradioactive surrogate for Pu3+, in iron borophosphate glasses/glass-ceramics (IBP glasses/glass-ceramics) has been investigated. The IBP glass containing 4 mol% Gd2O3 is homogeneously amorphous. At higher Gd2O3 concentrations, additional Gd is retained in the glasses as crystalline inclusions of monazite GdPO4 crystalline phase detected with X-ray diffraction. Moreover, Gd2O3 addition increases the Tg of the IBP glasses in glass formation range, which is consistent with the structural modification of the glasses. The structure of the Gd2O3-loaded IBP glasses/glass-ceramics is mainly based on pyrophosphate units. The chemical durability of Gd2O3-loaded IBP glasses/glass-ceramics is comparable to widely used borosilicate glass waste forms and the existence of monazite GdPO4 crystalline phase does not degrade the aqueous chemical durability of the IBP glasses/glass-ceramics. The Gd-loading results imply that the solubility should not be a limiting factor in processing nuclide Pu3+ if the formed crystalline phase(s) have high chemical durability.

Synthesis and study of bifunctional core–shell nanostructures based on ZnO@Gd2O3

Bifunctional nanostructures based on ZnO nanoparticles (NPs) with controlled Gd2O3 shell thicknesses were obtained by simple low-temperature methods (sol–gel technique and seed deposition method). The morphology, nanostructure, phase and chemical composition as well as luminescent and magnetic properties of the obtained core–shell nanostructures were investigated by transmission electron microscopy (HRTEM), energy dispersive x-ray spectroscopy (EDS), x-ray diffraction (XRD) techniques, optical spectroscopy, and SQUID magnetometer. As-obtained ZnO NPs are highly monodispersed and crystalline with mean particles size distribution of about 7 nm. Modification of the ZnO NPs surface by Gd2O3 shell leads to an increase of the ZnO particles size up to 80–160 nm and the formation the Gd2O3 shell with size of 2–4 nm. The dependence of the phase composition, luminescent and magnetic properties on Gd2O3 content are also discussed.

Highly sensitive and selective Gd2O3-doped SnO2 ethanol sensors synthesized by a high temperature and pressure solvothermal method in a microreactor

Gd2O3-doped SnO2 nanoparticles as highly sensitive and selective ethanol sensor materials with uniform size distributions were synthesized in ethylene glycol at 250°C and 20bar in a continuous tubular microreactor. The samples were characterized by DLS, XRD, SEM, EDX, TEM, FTIR, and BET surface area measurement techniques. As 5wt% Gd2O3 is added to SnO2, the average particle and crystallite sizes of the samples decrease from 22 and 11.9nm to 10 and 3.8nm, respectively. The responses of Gd2O3-doped SnO2 sensors containing 0–10.0wt% Gd2O3 calcined at 450°C were measured in presence of 300ppm CO, 10–1000ppm ethanol and 1.0 vol% of methane in air at 150–430°C. The sensor containing 10wt% Gd2O3 is highly sensitive and selective to ethanol in presence of CO, methane, and three volatile organic compounds, at 150°C. At the same low temperature, as the Gd2O3 content of the sensor increases from 2.5 to 10%, its response to ethanol dramatically enhances by about 263 times and the resistance in air changes by more than 4 orders of magnitude. Relative humidities higher than 50% eliminate the 10% Gd2O3–SnO2 sensor responses to CO and CH4 and the sensor shows absolute selectivity to ethanol.

Photostimulated luminescence properties of neutron image plates

The luminescence properties of two commercial neutron-sensitive image-plates based on Gd2O3-doped BaFBr:Eu2+ storage phosphors are examined. These are white Fuji plates and blue Fuji plates (BAS-ND) with Gd2O3 content by weight of 34% and 50%, respectively. Both plates show two maxima in the photostimulation spectrum near 500nm and 600nm, with the ratio of the peak responses (I600nm/I500nm) 1.39 and 0.53 for the white and blue plates respectively. The optimum wavelengths for photostimulation for the two phosphors are therefore different. The response of the blue plate is only 25% that of the white plate, if each is stimulated at its optimum wavelength.

Luminescence and Scintillation Response of Ce<sup>3+</sup>-Doped Oxide Glasses with High Gd<sub>2</sub>O<sub>3</sub> Content

This report presents the luminescence and scintillation response of Ce3+-doped oxide glasses with high Gd2O3 (30 mol%) content. The characteristic emission of Ce3+ 5d → 4f transition peaking around 380 nm was observed in its luminescence spectra under UV and X-ray excitation. Photoluminescence decay kinetics was governed by a few tens of nanoseconds decay time. The integral scintillation efficiency of about 22% of that of the Bi4Ge3O12 scintillator was obtained under X-ray irradiation. The light yield and its dependence on the integration time were measured and compared with that of the Bi4Ge3O12 crystal. The total mass attenuation coefficient at 662 keV γ-rays was also determined and compared with the theoretical one calculated using the WinXCom program.

Optical properties of Ce3+ doped fluorophosphates scintillation glasses

Fluorophosphates (P2O5–BaO–BaF2–Al2O3–Gd2O3–Ce2O3) glasses with different Gd2O3 and BaF2 concentrations have been prepared by a melt quenching method. The effect of Gd2O3 and BaF2 on the glass performance including the density, absorption as well as luminescence properties under both ultraviolet (UV) and X-ray excitation was studied systematically. Energy transfer from Gd3+ to Ce3+ plays an important role in the scintillation mechanism of these glasses and the optimum concentration of Gd2O3 is found to be approximately 3mol%. The highest integrated light emission intensity of these glass samples excited by X-ray is 25% of BGO and the decay time constants are in the range of 25–35ns, much shorter than the 300ns decay time of BGO. Meanwhile, replacing lighter compound BaO with the BaF2 can increase the density of the glasses and also improve the light yield.

Photo‐ and radioluminescence of Dy3+‐doped oxide glass with high‐Gd2O3 content

Dy3+‐doped oxide glass with 30 mol.% Gd2O3 content in the glass host was prepared by melt quenching under CO reducing atmosphere. The luminescence properties were investigated under UV and X‐ray excitation. The 4F9/2→6HJ (J = 15/2, 13/2, 11/2, and 9/2) luminescence was observed with intense blue (484 nm; 4F9/2→6H15/2) and yellow (576 nm; 4F9/2→6H13/2) emissions. Energy transfer from Gd3+ to Dy3+ ions was confirmed by photoluminescence excitation and emission spectra as well as photoluminescence decay measurements. The integral scintillation efficiency of 11% of Bi4Ge3O12 scintillator was obtained.

Raman, dielectric and variable range hopping nature of Gd2O3-doped K0.5N0.5NbO3 piezoelectric ceramics

(K0.5Na0.5)NbO3 (KNN) + x wt% Gd2O3 (x = 0 -1.5) ceramics have been prepared by conventional solid state reaction method. The effect of Gd2O3 on the structural, microstructural and dielectric properties of KNN ceramics were studied systematically. The effect of Gd2O3 on phase transformation from orthorhombic to psuedocubic structure is explained interms of changes in the internal vibration modes of NbO6 octahedra. The Raman intensity of the stretching mode v1 enhanced and shifted toward higher wavenumber with Gd2O3 concentration, which is attributed to the increase in polarizability and change in the O-Nb-O bond angles. Microstructural analysis revealed that the grain size of the KNN ceramics decreases from 2.26 ± 1.07 μm to 0.35 ± 0.13 μm and becomes homogenous with an increase in Gd2O3 concentration. The frequency dependent dielectric spectra are analyzed by using Havriliak-Negami function. The fitted symmetry parameter and relaxation time (τ) are found to be 0.914 and 8.78 × 10−10 ± 5.5 × 10−11 s, respectively for the sample doped with x = 1.0. The addition of Gd2O3 to the KNN shifted the polymorphic phase transition orthorhombic to tetragonal transition temperature (TO-T) from 199oC to 85oC with enhanced dielectric permittivity (ε′ = 1139 at 1 MHz). The sample with x = 1.0, shown a high dielectric permittivity (ε′ = 879) and low dielectric loss (<5%) in the broad temperature range (-140oC – 150oC) with the Curie temperature 307 oC can have the potential for high temperature piezoelectric and tunable RF circuit applications. The temperature dependent AC-conductivity follows the variable range hopping conduction mechanism by obtaining the slope -0.25 from the ln[ln(ρac)] versus ln(T) graph in the temperature range of 133 K-308 K. The effect of Gd2O3 on the Mott’s parameters such as density of states (N(EF)), hopping length (RH), and hopping energy (WH) have been discussed.

Effects of Gd3+: Ag co-doping on structural and magnetic properties of lead tellurite glass ceramics

Lead tellurite glass ceramics doped with variable amounts of Gd3+ ions and co-doped with fixed amounts of silver (Ag2O or Ag metallic nanoparticles, AgNPs) have been prepared and investigated by X-ray diffraction (XRD), density, electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. The EPR spectra of the studied samples exhibit the typical ‘‘U’’-type shape with effective g-values of ≈6, 2.8, 2.0 and a weaker feature at g≈4.8. At higher contents of Gd3+ ions the spectral features are broadened and finally are dominated by a broad absorption line located at g≈2.0 and a weaker feature at g≈6. The broad EPR line centered at g≈2.0 is associated to the Gd3+ ions present predominantly as clustered species. The paramagnetic susceptibility (χ) was measured at various temperatures and from the 1/χ versus T dependence the molar Curie constant (CM) and the paramagnetic Curie temperature (θp) have been evaluated. Magnetic susceptibility data show that for low Gd2O3 contents, x≤3mol%, the Gd3+ ions are randomly distributed in the host glass ceramics matrix and are present only as isolated species. For higher Gd2O3 contents, x>3mol%, the Gd3+ ions appear as both isolated and antiferromagnetically coupled species.

Neutronic effects of rhenium, gadolinia and uranium dioxide addition to a tungsten based fast spectrum space reactor

The neutronic effects of rhenium (Re), gadolinia (Gd2O3) and uranium dioxide (UO2) addition to a W–60vol.% UO2 fast spectrum fuel form were investigated relative to a prismatic reactor type using the MCNP5 Monte Carlo code with the ENDF/B-VII.1 cross-section database. The effects of rhenium addition to the cladding tubes and sleeves were studied over the range of 2–25at.% as well as the corresponding effects on the reactor mass and control drum reactivity swing and neutron energy spectrum. The effects of rhenium addition to the tungsten matrix over the range of 1–5at.% was also investigated. Lastly, the UO2 concentration was varied from 55 to 60vol.% UO2 and the UO2 was mixed with Gd2O3 at concentrations ranging from 2 to 10mol.%. Each configuration was investigated for its effects on the control drum shut down margin both in a dry state and in a submerged state where the reactor was surrounded and flooded with fresh water. The high thermal spectrum absorption cross-section of tungsten, rhenium and gadolinium proved excellent in maintaining the reactor in a subcritical state when submerged in fresh water. However, increases in the concentration of rhenium and gadolinia to the matrix, cladding and fuel kernels were also accompanied by an increase in reactor mass. The control swing within the drums was not influenced by the material compositions; however, the increase in reactor size with varying UO2 and Gd2O3 concentrations did prevent a large fraction of the neutron population from reaching the control drums. The decrease in neutron population with access to the reflector region containing the control drums caused a loss of reactivity swing in the drums by up to 2.8% Δk/k ($4.36).

Scintillation properties of Ce3+ doped SiO2-Al2O3-Gd2O3 glass

Scintillation glass is an attractive material due to its many advantages including low-cost and easy-manufacturing compared with single crystal. However the low density of glass scintillator restricts its applications. The introduction of heavy components such as PbO and Bi2O3 allows the density of the glass to be easily increased to more than 6.0 g/cm3 which is desirable for most applications. However, it is usually accompanied with a dramatic decrease in the luminescence response of Ce3+ ions. Although Gd2O3 based glass has a relatively high light yield, it is far below the high silica glass. In order to explain why the luminescent efficiency of Ce3+ doped glass with low density is high while that with high density is low, a glass-forming region of SiO2-Al2O3-Gd2O3 ternary system is achieved by high-temperature melt-quenching method. Ce3+doped SiO2-Al2O3-Gd2O3 and SiO2-Al2O3-Gd2O3-Ln2O3 (Ln=Y, La, Lu) scintillation glasses are prepared at reducing atmosphere. Their optical and scintillation properties are investigated. The results show that the content of Gd2O3 can reach as high as 30% mol without phase separation. In addition, the UV cut-off position is red-shifted, PL intensity decreases and decay time reduces from 70 to 37.6 ns with increasing the Gd2O3 concentration. After Lu2O3, La2O3, Y2O3 are added in the glass, the UV cut-off position is red-shifted and PL intensity decreases. Moreover the UV cut-off position is in the order of La>Y>Lu and the decay time is in the order of La2O3 is more than 10% mol, X-ray excited luminescence light emission intensity reduces from 61% of BGO to 13% of BGO. With the UV cut-off position red-shifted, the bandgap of glass becomes narrow, resulting in the 5 d level of Ce3+ ions gradually approaching to the conduction band and the 5 d electrons easily combining with the holes in the glass through the conduction band. Namely, charge transferring quenching occurs. This is the reason why the PL intensity and decay time both decrease. It can also explain why the luminescent efficiency of Ce3+ doped glass with low density is high while that with high density is low.

Luminescence properties of Gd3+-doped borosilicate scintillating glass

Gd3+-doped borosilicate glasses are prepared in different melting atmosphere. Absorption spectra, decay time, luminescence spectra under UV and X-ray excitation are investigated. With melting atmosphere changing from air to CO, the luminescence intensities of Gd3+ at 313nm under the excitation of UV and X-ray are both enhanced. This mainly results from the reduction of Gd3+, which is validated by electron paramagnetic resonance (EPR). The optimal Gd2O3 content for the glasses prepared under CO atmosphere is 7.5mol%, whose integral scintillation efficiency is 20% compared with Bi4Ge3O12.

Electrical properties of silicate glasses of low level gadolinium oxide doping including dielectric and infrared measures

Glasses of the composition (mol%) 15Na2O, 20CaO, 65SiO2 doped with low contents of Gd2O3 (0.14–0.83 × 10−2 mol per 100 g glass) were prepared by the melt quenching method. The effect of Gd2O3 content on the electrical, dielectric and infrared properties of the silicate glass was studied. The Gd2O3 content in the silicate glass provides more non-bridging oxygen atoms into the micro structure, yet the strong field strength of Gd3+ ions in this glass has a counter effect that leads to a contraction in its micro structure. This contraction leads to decrease of water bands in the IR transmittance spectra. Gd2O3 increases the conductivity σac which is due to ionic and electronic carriers. Variation of log σac as a function of frequency shows a hopping frequency (ωh) that occurs at lower frequency values as mol of Gd2O3 content was increased. The real part of the dielectric constant (e′) for glass containing 0.0083 mol Gd2O3 shows a value of 450 at 1 kHz which may make it as a promising candidate for energy storage in electronic applications.

Effect of Concentration and Temperature on the Surface Morphology of Gd2O3 Nanocrystallites in Silica

Gd(NO3)3.6H2O and TEOS were used as precursors and obtained Gd2O3:SiO2 ceramic powder having different concentration of Gd2O3 as 2.2, 2.8, 3.4, and 4.0 wt % using solgel process. The powdered samples were annealed at 500°C and 900°C temperatures and characterized by XRD, FTIR, SEM, and TEM. In X‐ray diffraction, cubic phase of Gadolinium oxide is reported only for the annealed samples having higher concentration (3.4 & 4.0 wt %) of Gd2O3. SEM and TEM results further confirm that the surface morphology of the microstructures depend on the temperature and concentration.