Gd2O3 Content Research Articles

Melt grown ZrO2 single crystals partially stabilized with Gd2O3: Phase composition and indentation induced transformations

Abstract ZrO2 solid solution crystals partially stabilized with Gd2O3 in the 2.0 to 4.0 mol% concentration range have been grown using the directional melt crystallization in a cold crucible. We show that the crystals have a homogeneous distribution of the components along the length of the crystal, and their chemical composition corresponds to that of the initial charge. The phase composition of the crystals has been studied using X-ray diffraction. The local phase composition in the vicinity of the indentation has been studied using Raman spectroscopy. The microhardness and fracture toughness of the crystals have been studied by indentation. The correlation between the fracture toughness of the crystals and their phase composition and indentation induced transformations has been discussed. We show that an increase in the Gd2O3 concentration in the crystals from 2.8 to 4.0 mol% reduces the content of the transformable tetragonal t phase, its tetragonality degree and the intensity of the indentation induced tetragonal to monoclinic phase transition. These factors are known to eventually reduce the fracture toughness of the crystals with an increase in the Gd2O3 concentration.

Microstructure and its effect on mechanical and thermal properties of Al-based Gd2O3 MMCs used as shielding materials in spent fuel storage

In this study, novel Al-based Gd2O3 metal matrix composites were designed and synthesized using powder metallurgy to overcome the shortcomings of common neutron absorbers used as shielding materials in spent fuel storage. With an increase in the ball-milling time, the size of powder particles was gradually refined to nanometer scale. Meanwhile, monoclinic Gd2O3 was induced by collision pressure and, according to dynamic analysis, the solid solution was inconspicuous. Al3Gd and Gd3Al5O12 were formed during ball-milling, which was further accelerated during sintering because thermodynamics analysis indicated that the reaction was endothermic. The microstructures of powder mixtures and sintered bulks were seen. Particles of various shapes were found to be dispersed in the bulk matrix; their shapes and sizes varied with milling time, sintering time and temperature, and concentration of Gd2O3. With the increase in sintering temperature and time, the number of porosities and nanoparticles were found to decrease, whereas the sizes of the particles increased. The microhardness of the samples prepared under various conditions was measured, and its relationship with the microstructure was analyzed. It was found that microhardness was positively correlated with the areas of the particles, whereas it was negatively correlated with their sizes. Further, the thermal parameters of the sintered bulks were also measured and the effect of their microstructure and components was analyzed.

EFFECT OF Gd2O3 DOPING ON DIELECTRIC PROPERTIES OF Ba(Zr0.1Ti0.9)O3 CERAMICS

Using BaCO3, TiO2, ZrO2 and Gd2O3 as the starting materials, the Ba(Zr0.1Ti0.9)O3 ceramics are prepared using solid state synthesis method, and effects of Gd2O3 dopant on microstructure and dielectric properties of Ba(Zr0.1Ti0.9)O3 ceramics are investigated. The results show that the crystal structure for Ba(Zr0.1Ti0.9)O3 ceramics is a single perovskite structure, and the doping of Gd3+ does not generate new phase. With the Gd2O3 concentration increasing, the grain size increases continuously, when the doping amount x ≥ 0.5 mol %, the grain size basically remains unchanged, the grain size is uniform. With the Gd2O3 content increasing, the dielectric constants rose first and then decreased under different sintering conditions of 1280 °C, 1300 °C, 1330 °C, and 1350 °C. When the sintering temperature is 1350 °C and the Gd3+ doping amount is x = 0.5 mol %, the dielectric loss is minimal, the dielectric constant is the highest, and the dielectric performance at room temperature is optimal. Gd2O3 doping has little effect on the movement of the Curie point of BZT ceramics, but the doping of Gd2O3 can increase the peak of the dielectric peak at the Curie point.

Optical and thermal properties of TeO2–B2O3–Gd2O3 glass systems

Abstract New glass samples with composition (1 – x)[(TeO2)70(B2O3)30] – x(Gd2O3) with x = 0.2, 0.4, 0.6, 0.8 and 1.0 in mol% have been synthesized by conventional melt-quenching techniques. X-ray diffraction (XRD) studies were performed in order to confirm the amorphous nature of the samples. The density of the samples has been found to vary with the Gd2O3 content, whereas an opposite trend has been observed in the molar volume. The analysis of Fourier Transform Infrared (FT-IR) spectroscopy of the samples showed that the glass network is mainly built of TeO3, TeO4, BO3 and BO4 units. The addition of Gd2O3 changed the refractive index, optical band gap and Urbach energy of the glass samples. The thermal properties of the studied glasses were investigated by measuring the thermal diffusivity of the samples by using photoflash method at room temperature.

Physical, structural, optical, and radiation shielding properties of B2O3–Gd2O3–Y2O3 glass system

In the current paper, glass samples were prepared from the composition xGd2O3–(30-x)Y2O3–70B2O3 (where x = 5, 10, 15, 20 and 25 mol%) via the technique of melt-quenching. Various optical parameters and inter-atomic separation were evaluated for the fabricated samples. The results showed that the inter-substitution of Y2O3 content in replacement with Gd2O3 content in the glass matrix shows structural variation in the glass. The density increases from 3.5521 to 4.1613 g/cm3 with increase in Gd2O3 content that signifies the role of Gd2O3 being a glass modifier. The transmission spectra of the glass sample show more than 85% transmittance suggesting their superior transparency in the visible region. Also, several important shielding parameters of the prepared glass system have been computationally determined via the Geant4 model and the results were compared with Phy-X/PDS database software. The results revealed that the mass attenuation factor (µ/ρ) obtained by utilizing the two different toolkits are in agreement. The transmission fraction and the half value layer parameters of the glass system indicate that the glass sample with higher Gd concentration provides a better gamma blocking ability thanks to the high atomic number of Gd.

Luminescence and scintillation properties of Ce3+-doped SiO2–Al2O3–BaF2–Gd2O3 glasses

Ce3+-doped glasses with composition of (65-x)SiO2 − 20Al2O3 –15BaF2 -xGd2O3 (x = 5, 10, 15, 20 and 25) were synthesized under CO atmosphere by melt-quenching method. The photoluminescence (PL) emission due to Ce3+: 5d1 → 4f transition was red-shifted with increasing Gd2O3 content. The acceleration of PL decay was observed with increasing Gd2O3 content. The scintillation efficiency of about 100% of the Bi4Ge3O12 scintillator was obtained for a 10%Gd2O3 containing glass while a high light yield (LY) of 2050 photons/MeV and energy resolution of 15.8% at 662 keV γ rays was obtained for a 15%Gd2O3 containing glass. The integrating-time dependence of LY value and LY ratio (α/γ ratio) under excitation with α- and γ-rays were also measured.

An extensive investigation of physical, optical and radiation shielding properties for borate glasses modified with gadolinium oxide

We prepared four Gd2O3 doped borate glasses and investigated their physical, optical and radiation shielding features. The density of glass samples was increased linearly with the Gd2O3 content. The transmission spectra of the samples show more than 85% transmittance suggesting their superior transparency in the visible region. The band gap decreases with increase in Gd2O3 content. The Geant4 code was used to find the attenuation factor for the samples between 0.284 and 2.506 MeV. The results demonstrated that the transmission factor changes from 51% (corresponding to 20 mol% of Gd2O3) to 39% (for 35 mol%) at 0.284 MeV. The addition of Gd2O3 affects highly the mass attenuation parameter at 0.284 and 0.347 MeV. The effective atomic numbers of the glass sample corresponding to 20 mol% of Gd2O3 are in the range 12.06–18.79. The maximum tenth value layer was observed for 20 mol% of Gd2O3 sample (15.768 cm).

Ionic conductivity, phase composition, and local defect structure of ZrO2-Gd2O3system solid solution crystals

The crystalline structure, ionic conductivity, and local structure of ZrO2-Gd2O3solid solution crystals have been studied for a wide range of compositions. The (ZrO2)1-х(Gd2O3)хcrystals (x = 0.03–0.33) have been grown by directional melt crystallization in cold crucible. The phase composition of the crystals has been studied using X-ray diffraction and transmission electron microscopy. The transport parameters have been studied using impedance spectroscopy in the 400–900 °С range. The local structure of the crystals has been studied by optical spectroscopy with Eu3+ ion probe. The maximum conductivity at 900 °С (0.047 S/cm) has been observed in the crystals containing 10 mol% Gd2O3. This composition is close to the cubic/tetragonal phase boundary. The compositions corresponding to the single-phase cubic region exhibit a decrease in the ionic conductivities with an increase in the Gd2O3 concentration. Studies of the local structure of the ZrO2-Gd2O3 system solid solutions have revealed specific features of the formation of optical centers which characterize the localization of oxygen vacancies in the lattice depending on the concentration of the stabilizing oxide. Comparison of the experimental values of the lattice parameter with those calculated using various models has shown that the best fit between these data is provided by the model of inequiprobable distribution of oxygen vacancies. We have discussed the correlation between the crystalline and local structures and the transport parameters of the crystals. Analysis of the results allows us to identify the Gd2O3 concentration ranges in which the ionic conductivity of the crystals is mainly determined either by the phase composition or by the regularity of oxygen vacancy localization in the crystal lattice.

Influence of gadolinium oxide and ulexite on cement hydration and technical properties of mortars for neutron radiation shielding purposes

Gadolinium oxide (Gd2O3) is a potentially effective mineral additive that improves neutron shielding properties of cement based composites. The paper presents the influence of Gd2O3 and ulexite (a boron compound) on Portland cement hydration evaluated by isothermal calorimetry measurements and strength. The progress of hydration was investigated on mortar specimens at water to cement ratio w/c = 0.5 and sand/cement ratio 0.75. The addition of Gd2O3 generates a slight retardation of cement hydration, however it accelerates aluminate activity at the same time. The hydration of cement was completely hindered for mortars containing a substantial content of ulexite. The strength test results show that addition of Gd2O3 to Portland cement mortar mix caused a decrease of early age (3 days) flexural and compressive strength. The optimum content of Gd2O3 in respect to the long term compressive strength and the hydration kinetics was 5% in relation to the mass of cement. Good long term strength was also obtained for specimens with 3% of ulexite.

The Gd2O3 effect study on properties of CaGdSiB:Tb3+ glass for photonics applications

Tb3+ doped calcium gadolinium silica borate glasses (CaGdSiB:Tb3+) were prepared to study the influence of Gd2O3 concentration on physical, glass network, optical and luminescence properties. Glass density and molar volume increased with increment of Gd2O3 concentration. The enlargement of molar volume and evolution of FTIR spectra confirmed the non-bridging oxygen more occurring in glass network with increment of Gd2O3. Tb3+ in glass absorbed photons in visible light and near-infrared region. Glass exhibited the strongest luminescence intensity of Tb3+ at 542 nm under 275 nm excitation, passing through the Gd3+ - Tb3+ energy transfer. The overall color of emission is green in CIE 1931 chromaticity. The emission intensity did not show clear relation with Gd2O3 concentration. However, glass with 22.5 mol% of Gd2O3 possessed the highest emission intensity. The luminescence decay times of Tb3+ was about 2 ms which decreased via increasing of Gd2O3 content. CaGdSiB:Tb3+ glass performs the potential for using as a scintillator for detector with integration mode and a green light source medium.

Catalytic Properties of Gadolinium Oxide in the Removal of Doxycycline with Anticancer Activity

We located multiple binding sites for doxycycline on DNA under physiological conditions, using spectroscopic methods and molecular modeling. Fourier-transformed infrared spectroscopy and UV-visible spectroscopy are used to determine the ligand intercalation and external binding modes, the binding constant, and the stability of doxycycline–DNA complexes in an aqueous solution. Spectroscopic evidence shows that the doxycycline (DOXY) complexation with DNA occurs via G–C and A–T, and a PO2 group with a binding constant K(DOXY–DNA) = 1.4×104 M–1. Uniform rare-earth gadolinium oxide (Gd2O3), as formed through a precipitation process using hexamine as template, are characterized using X-ray diffraction and scanning electron microscopy. Another aim of the study was to investigate the degradation of the DOXY antibiotic by nanosized Gd2O3 under ultraviolet irradiation. Various experimental parameters such as initial DOXY concentrations, initial Gd2O3 concentration, initial pH, reaction times are investigated. According to the results, this method can be good in the removal of DOXY.

Wear Resistance Mechanism of Alumina Ceramics Containing Gd₂O₃.

Excellent wear resistance of alumina ceramics is a desirable quality for many products. The purpose of this work was to improve the wear resistance of 99% alumina ceramics in an Al2O3–Gd2O3–SiO2–CaO–MgO (AGSCM) system. The content of Gd2O3 varied from 0.01% to 1%. A test of wear rate was performed in a ball milling apparatus in a water environment according to the Chinese industry standard. The compositions and microstructure of this material, as well as the effect of bulk density on wear rate, were studied. The effect of Gd2O3 on phases, grain growth mode, and grain boundary cohesion was investigated. It was found that Gd2O3 could refine grain size, form compressive stress of the grain boundary, and promote the crystallization of CaAl12O19. The wear rate of this material was as low as 0.00052‰ (the Chinese industry standard wear rate is ≤0.15‰). The mechanisms for wear resistance of AGSCM ceramics were also determined.

Impact of integral burnable absorbers on SMART reactor behaviour under normal and anomalous operational conditions

Burnable poisons are used to safely prolong reactor core cycle time. They are effective alternatives to regulate power peaking factor and to reduce soluble boron concentration. One of common materials employed for this purpose is Gd2O3 dispersed homogenously in UO2 fuel material. The amount of Gd2O3 content impacts directly on thermophysical properties of integral burnable absorber rods. Therefore, especial care must be taken at the design stage of the reactor core. In this paper, the effects of various Gd2O3 contents, as a burnable poison, on neutronic and thermal hydraulic behaviour of a SMART reactor are investigated. MCNPX 2.6 code is used to perform neutronic simulations of the core. The COBRA-EN with modified MATPRO subroutine is employed for calculating integral burnable absorber rods temperature in normal operation and control rod withdrawal accident. Results show that 12 percent of weight fraction for Gd2O3 lead to the suitable neutronic design which does not break the thermal hydraulic and safety constraints. The performance of the core design is evaluated in steady state and transient conditions in details in the paper.

Synthesis and Physicochemical Properties of Nanopowders and Ceramics in a CeO2–Gd2O3 System

Nanopowders with a composition of (СeO2)1–x(Gd2O3)x (x = 0.03, 0.05, 0.07, and 0.10) are synthesized by the coprecipitation method using cryotechnologies. The coherent scattering region (CSR) of the powders is 10–14 nm and the specific surface area is 70–81 m2/g. Based on the powders, ceramic nanosized materials with CRS of 64–71 nm are obtained. The dependence of the phase composition, microstructure, and electrical transport properties of the obtained samples on the Gd2O3 content is established. In a CeO2–Gd2O3 system, a solid solution with the composition of (CeO2)0.90(Gd2O3)0.10 has the highest ionic conductivity with the transfer number of ions of ti = 0.74 at a temperature of 700°C. It is shown that ceramics of this composition can be used as a solid electrolyte of intermediate-temperature fuel cells due to their physicochemical characteristics.

Influence of Gd2O3 on thermal and spectroscopic properties of aluminosilicate glasses

A series of aluminosilicate glasses 25SiO2·(20-x)Al2O3·40Na2O·15BaO-xGd2O3 with 0 ≤ x ≤ 10 were prepared in order to analyze the influence of gadolinium on thermal and spectroscopic properties of these materials. Increasing of thermal parameters (Tg, Tx, Δcp, ΔT) values with higher Gd2O3 content was determined using DSC method. Crystalline phases, formed during heat treatment, were identified with XRD - NaAlSiO4 and BaSiO3 in glass with 0% mol. Gd2O3 and Gd9.33(SiO4)6O2, NaAlSiO4 and BaAl2Si2O6 in glass with 10% mol. Gd2O3. Spectroscopic analysis – FTIR and Raman – revealed Gd2O3 influence on glass structure in the same way like Al2O3, but some differences appear due to the differ bond strength and ionic radius between Gd and Al. Raman spectra confirmed higher network polymerization (enriched with Q2 units). Optical band gap energy (Eopt) and Urbach energy (ΔE) were calculated from the Tauc plot. Mechanical tests demonstrated lower microhardness with increasing content of Gd2O3 content, as a result of higher concentration of atoms with larger radius.

A study of the magnetic susceptibility on gadolinium calcium silicoborate glass

The aim of this study is to explore the magnetic susceptibility of gadolinium-based glass having the composition: (80−x) B2O3-10SiO2-10CaO-xGd2O3 (where x = 20, 25, 30 and 35 mol%) The results show that the density of glass samples increases with increased concentrations of Gd2O3. The magnetic susceptibility of glass samples, which is represented by magnetic resonance signal intensity, varies directly with the concentration of Gd2O3 in gadolinium calcium silicoborate glass. Signal to noise ratio (SNR) in T1 were increased when concentration of Gd2O3 increased. This study found that gadolinium calcium silicoborate glass can be selected as a good choice for determining magnetic susceptibility in further MRI studies.

Development of gadolinium doped calcium phosphate oxyfluoride glasses for X-ray shielding materials

In this work, gadolinium calcium phosphate oxyfluoride glasses in the compositions of 10CaF2:xGd2O3:(90-x)P2O5 where x was the concentration of Gd2O3 at 5, 10 and 15 mol% have been prepared using melt-quenching method and investigated physical properties, optical properties and X-ray shielding properties. The density and molar volume of glasses were increased with increasing of Gd2O3 concentration. The optical spectra of the glasses show the high transparency in visible region. The X-ray shielding properties were studies at energy range 50-120 kVp. The results showed that the total mass attenuation coefficients increased with increasing of Gd2O3 concentration and decreased with increasing X-ray energy. The half value layer (HVL) and the tenth value layer (TVL) were decreased with increasing of Gd2O3 concentration and increased with increasing of the voltage, Lead equivalent thickness values increased with increasing of Gd2O3 concentration and show the two increasing trend with X-ray energy. These results indicating the potential of the prepared material as X- ray shielding material.

Photocatalytic activity of Ag/Al2O3-Gd2O3 photocatalysts prepared by the sol-gel method in the degradation of 4-chlorophenol.

The photocatalytic activity in the degradation of 4-chlorophenol (4-ClPh) in aqueous medium (80 ppm) using 2.0 wt% Ag/Al2O3–Gd2O3 (Ag/Al–Gd-x; where x = 2.0, 5.0, 15.0, 25.0 and 50.0 wt% of Gd2O3) photocatalysts prepared by the sol–gel method was studied under UV light irradiation. The photocatalysts were characterized by N2 physisorption, X-ray diffraction, SEM, HRTEM, UV-Vis, XPS, FTIR and fluorescence spectroscopy. About 67.0% of 4-ClPh was photoconverted after 4 h of UV light irradiation using Ag/γ-–Al2O3. When Ag/Al–Gd-x photocatalysts were tested, the 4-ClPh photoconversion was improved and more than 90.0% of 4-ClPh was photoconverted after 3 h of UV light irradiation in the materials containing 15.0 and 25.0 wt% of Gd2O3. Ag/Al–Gd-25 was the material with the highest efficacy to mineralize dissolved organic carbon, mineralizing more than 85.0% after 4 h of UV light irradiation. Silver nanoparticles and micro-particles of irregular pentagonal shape intersected by plane nanobelts of Al2O3–Gd2O3 composite oxide were detected in the Ag/Al–Gd-25 photocatalyst. This material is characterized by a lowest recombination rate of electron–hole pairs. The low recombination rate of photo-induced electron–hole pairs in the Ag/Al–Gd-x photocatalysts with high Gd2O3 contents (≥15.0 wt%) confirmes that the presence of silver nanoparticles and microparticles interacting with Al2O3–Gd2O3 composite oxide entities favors the separation of photo-induced charges (e− and h+). These materials could be appropriate to be used as highly efficient photocatalysts to eliminate high concentrations of 4-ClPh in aqueous medium.

Structure, densification and electrical properties of Gd3+ and Cu2+ co-doped ceria solid electrolytes for SOFC applications: Effects of Gd2O3 content

Ceria-based solid electrolytes exhibit superior electrical conductivity compared to traditional yttria-stabilized zirconia ceramics. However, they require high sintering temperatures to achieve full densification. Transition metal oxides exhibiting low melting points, such as CuO, have been used as additives to lower the sintering temperature of these materials. In this context, the present work is focused on the evaluation of the effects of gadolinium oxide (Gd2O3) content on the structure, densification and electrical properties of ceria co-doped with CuO. Nominal compositions of Ce0.99−xGdxCu0.01O2-δ (0 ≤ x ≤ 0.3) were synthesized by the polymeric precursor method. The precursor powders were characterized by simultaneous thermogravimetry and differential thermal analysis (TG/DTA) and the calcined powders were studied by X-ray diffraction (XRD) and Rietveld refinement to obtain crystallographic parameters. The sinterability of green bodies was evaluated by dilatometry up to 1200°C. The relative density was determined in samples sintered between 950 and 1050°C and the microstructural characterization was performed by scanning electron microscopy (SEM). The electrical properties were investigated by impedance spectroscopy (IS). The XRD results confirms the formation of a cubic fluorite type structure in the entire composition range. The lattice parameters obtained by Rietveld refinement showed a reduction in the crystallite size with increasing gadolinium content. Densification was improved with increasing Gd-content up to x = 0.15. The electrical conductivity was enhanced by gadolinium addition, reaching a maximum of 7.81mScm−1 at 600°C for the composition x = 0.15 sintered at a temperature as low as 1050°C.

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+.