Phase Of Gd2O3 Research Articles

Predicting the stability and exploring the fundamental physical properties of tetragonal Gd2O3: A comprehensive first-principles investigation

A burnable absorber is a material used in nuclear reactors to manage reactivity and extend operational cycles by absorbing neutrons. Gadolinium oxide (Gd2O3) is a prevalent burnable absorber employed in nuclear reactors. By utilizing density functional theory (DFT) within a first-principles framework, a comprehensive exploration into the physical characteristics of the predicted tetragonal phase of Gd2O3 has been effectively conducted. The investigation encompasses structural, electronic, magnetic, elastic, mechanical, bonding, thermophysical, and optical aspects. Since tetragonal Gd2O3 has not been experimentally synthesized, the stability of the tetragonal phase is confirmed through assessments of its structural, lattice dynamical, thermodynamic, and mechanical attributes. Demonstrating semiconducting behavior, the electronic nature reveals a band gap of 1.241 eV. The density of states (DOS) illustration validates the semiconductor electronic character, and the calculated magnetic moment, determined through up-down spin DOS, is 3.06 μB/f.u. The Poisson’s ratio value reflects the dominance of ionic bonding in Gd2O3, a finding corroborated by bond population analysis. Impressively, the tetragonal Gd2O3 displays elevated lattice thermal conductivity value in comparison to its cubic, monoclinic, and hexagonal counterparts. Furthermore, the determined melting point registers at 1709.31 K. In the realm of optics, an analysis based on frequency dependence reveals that tetragonal Gd2O3 holds promise as a candidate for optoelectronic applications, particularly in the ultraviolet (UV) energy range.

Exploiting the combined power of C3N4/Ti3C2/Gd2O3 nanocomposites for advanced ciprofloxacin and pathogen degradation in wastewater

Using a solvothermal method, C3N4/Ti3C2/Gd2O3 (CN-TC/GdO) nanocomposites were synthesised and characterised using various methodologies. In the composite material, the XRD analysis revealed the presence of C3N4, Ti3C2 and Gd2O3 phases. The SEM and TEM images confirmed that nanocomposites with a homogenous and compact structure were successfully synthesised. UV-Vis spectroscopy revealed that the nanocomposites exhibited outstanding visible region absorption, which is advantageous for photocatalytic applications. Using ciprofloxacin as a model pollutant, the photocatalytic activity of the nanocomposites was evaluated, and the results indicated that the CN-TC/GdO nanocomposites exhibited substantially enhanced degradation efficiency compared to the individual components. The increased photocatalytic activity can be attributed to the synergistic effects of the three components, which function as efficient electron acceptors and donors and provide surface area and charge transfer pathways. Antibacterial activity was observed in CN-TC/GdO nanocomposites. These results indicate that CN-TC/GdO nanocomposites have tremendous potential as a photocatalytic material for the removal of ciprofloxacin from aqueous solutions and antibacterial research.

Mechanosynthesis and electrical conductivity of undoped and calcium-substituted GdAlO3 perovskites

Gadolinium aluminate (GdAlO3) and its calcium-substituted derivates (Gd1-xCaxAlO3-δ; x = 0.05, 0.10 and 0.15) are prepared via one-step mechanochemical processing of simple oxide precursors at ambient temperature. The mechanochemical reaction is accompanied by Gd2O3 phase transformation. The as-prepared and sintered materials are characterized by X-ray diffraction and scanning electron microscopy. Sintering at 1450 °C resulted in relatively porous ceramics (with density <90 % of theoretical value) except Gd0.85Ca0.15AlO3-δ. The electrical conductivity of the sintered samples was investigated by impedance spectroscopy at 350–1000 °C in air. Undoped GdAlO3 ceramics exhibit low conductivity, ∼10−6 S/cm at 800 °C. Acceptor-type substitution of 5 at % of gadolinium by calcium results in ∼3 orders of magnitude increase in both total and bulk conductivity associated with a substantial enhancement in oxygen-ionic transport. Further doping has a limited effect on the electrical transport properties, and electrical conductivity remains nearly composition-independent in the range x = 0.05–0.15. Grain boundaries are demonstrated to have a significant contribution to the total resistivity of prepared calcium-substituted Gd1-xCaxAlO3-δ ceramics with grain sizes in the range of 1.1–1.5 µm.

Effect of yttria substitution on structure, optical and mechanical properties of (Gd, Y)2O3–MgO nanocomposite ceramics

A citrate-nitrate combustion method was applied to synthesize fine composite Gd2-xYxO3-MgO (x = 0, 0.02, 0.2, 0.3, 0.4, 0.6) nanopowders. Y2O3 substitution inhibited Gd2O3 phase transition from cubic structure to monoclinic structure during sintering, thereby stabilizing its cubic structure to room temperature. This approach led to nanocomposite ceramics with a grain size of about 190 nm and increased the transmittance to 85% over the 3–5 μm wavelength range when x = 0.3. However, the addition of Y2O3 weakened the mechanic properties of the nanocomposite ceramics.

Synthesis and Characterizations of Gd1.99Ce0.01O3 Phosphors

The present research aims to study the structural, morphological and bandgap studies of 1mol% Ce doped Gd2O3 samples. Gd1.99Ce0.01O3 sample was synthesized via hydrothermal method. The crystallinity, phase and crystallite size are determined using X-ray diffraction (XRD) patterns. X-ray diffraction patterns revealed the development of pure crystalline phase Gd2O3 sample. The morphology of the synthesized sample is examined using Field emission scanning electron microscope (FESEM) micrographs and elemental composition by energy dispersive spectroscopy (EDS) spectra. FESEM results confirmed the formation of rod shape of the synthesized samples. The bandgap studies are done using UV-Visible spectroscopy. The synthesized samples are the potential candidates for various biomedical, and optoelectronic applications.

The influence of lithium ion incorporation on the luminescence enhancement of Gd2O3:Pr3+ nanophosphors for lighting applications

In this study, nanosized Gd2O3: Pr3+ and Li+ co-doped Gd2O3: Pr3+ were synthesised by solution combustion method for analysing the structural, morphological and optical properties. X-ray diffraction patterns of as-prepared Gd2O3:Pr3+ indicated the existence of multiphase crystallites and it transformed to pure cubic phase upon annealing. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) images confirmed that the particles are spherical. Upon 321 nm excitation, Gd2O3: Pr3+ phosphor exhibits characteristic emission bands at 613 nm, 529 nm and 439 nm. The photoluminescence emission intensity was found maximum for 2 wt% Pr3+ doped Gd2O3 powders. Li+ ions were co-doped into this Gd2O3:Pr3+ phosphor and were found to induce a considerable enhancement in PL emission intensity. Lithium co-doped samples crystallize in cubic structure. Raman spectra of the Li+ co-doped phosphors revealed characteristic Ag+ Fg mode of the cubic phase of Gd2O3, apart from other independent modes. The maximum emission intensity was obtained for 0.5 wt% Li+ co-doped samples, with an improved intensity of about 2.87 times that of Gd2O3:Pr3+. The new composition Gd2O3: Pr3+: Li+ with enhanced luminescence properties can be employed as a red light emitting phosphor for white light emitting diodes (WLEDs).

Microstructure and mechanical properties of Mg–Ni–Gd alloy synthesised by powder metallurgy

ABSTRACT The hexagonal close-packed structure renders magnesium weak at room and high temperatures for structural applications despite its low density. Inducing thermally stable and coherent second phases would enhance/retain the strength of Mg-based alloys even at high temperatures. This paper aims to develop a high-strength Mg-based nanocomposite. A master alloy composed of Ni and Gd was cast and the composition of Mg97.56Ni1.22Gd1.22 (at.-%) was prepared using ball milling for 150 h. XRD plots of the as-milled powder having nano-size crystallites confirm the partial dissolution of the master alloy. Consolidation through sintering with 5, 7 and 9 h of exposure at 550°C and extrusion at 500°C resulted in the formation of Mg5Gd, Mg2Ni, Gd2O3 and MgO phases. The extruded samples possessed a high strength of 804 MPa, which can be attributed to ultra-fine grains and dispersoid strengthening by homogeneously distributed second-phase particles in the 100–200 nm range.

Band gap and pseudocapacitance of Gd2O3 doped with Ni0.5Zn0.5Fe2O4

Herein, we present a detailed study of the structural, optical, and electrochemical responses of Gd2O3 doped with nickel zinc ferrite nanoparticles. Doping of Ni0.5Zn0.5Fe2O4 nanoparticles to Gd2O3 powder was done through thermal decomposition at 1000 °C. The average grain size of the mixture was determined to be approximately 95 nm, and phases of cubic Gd2O3, GdO, and orthorhombic prisms of GdFeO3 were identified. The focused ion beam energy dispersive x-ray spectrum (FIB-EDX) mapping results clearly show the morphology of the particles with Gd and Fe as the dominant elements. The structural data were compared with the spectroscopic measurements confirming the formation of multiple phases of oxides and ferrites. The measured optical band gap is significantly redshifted to 1.8 eV and is close to that of nitride compounds of gadolinium metal. The measured specific capacitance was almost 7 Fg−1 at a current density of 1 Ag−1, showing a small drop of 27% when the current density is increased to 10 Ag−1. Cyclic voltammetry (CV) plots of the ferrite doped Gd2O3 electrode at a scan rate of 5 to 100 mV s−1 indicate the pseudocapacitive nature of the material.

Shrinkage features, microstructure evolution and properties of Gd2O3-MgO optical composite ceramics with Zr as phase stabilizer

A novel composite ceramic, composed of equal-volumetric Zr-stabilized Gd2O3 and MgO phases, was prepared to be transparent in mid-wave infrared range. Zr stabilized Gd2O3 is proved to have a lower lattice parameter (10.7516 Å) using XRD refinement. Pressureless sintering behavior of Gd2O3-MgO with/without 2 at% Zr-doping (naming ZGM and GM) was studied via the real-time observation technique. The shrinkage of ZGM green body proceeds steadily up to 1400 °C while that of the undoped one shrinks sharply at 1250 °C due to Gd2O3 phase transition. The segregation of Zr element along the grain boundaries of Zr-Gd2O3 creates a synergized effect on the grain refinement with pinning effect. Dense ZGM ceramics exhibit superior transmittance of 78.3 %‐85.6 % at 3–5 µm, which show good consistency with the calculated values. The refractive index of Zr- Gd2O3 varies from 1.87 at 3 µm to 1.80 at 5 µm, which is smaller than those of monoclinic Gd2O3.

Redshift of the optical gap in ferrite doped Gd2O3

We report the measurement of the optical bandgap in ferrite doped Gd2O3. Doping of the nickel zinc ferrite (Ni0.5Zn0.5Fe2O4) nanoparticles to Gd2O3 powder was done through thermal decomposition of the mixture at 1000 °C. The average grain size of the thermally decomposed mixture was determined to be around 95 nm and contained phases of cubic Gd2O3, GdO, and orthorhombic prisms of GdFeO3. The imaginary part of the complex dielectric function was calculated from the absorbance measurements that showed an optical bandgap at 1.8 eV. The observed value of the fundamental energy gap is on average 4.0 eV smaller than suggested by early experiments. A model for the ferrite doped Gd2O3 was constructed to suggest that the Ni, Zn, and Fe atoms occupy Gd sites in the Gd2O3 lattice. A new band at Γ point is formed due to the hybridization of the atomic orbitals of dopant and Gd3+ that shifts the fundamental absorption edge to the red part of the photon energy spectrum. Despite having a high density of negatively charged carriers contributed by the dopant, the onset of the direct interband transitions is clearly resolved.

Bi3+ sensitized Gd2O3:Eu3+: A potential red phosphor for UV LED pumped white light emission

Bi3+ sensitized Gd2O3:Eu3+ phosphors were synthesized by hydrothermal method using polyvinylpyrrolidone as capping agent. As-prepared samples exhibit crystalline hexagonal phase Gd(OH)3. While post annealing at 900 °C, Gd(OH)3 transforms to cubic phase Gd2O3. The lattice substitution by Bi3+ in different symmetry sites, viz. C2 and S2 of Gd2O3 leads to 2 (two) prominent excitation bands related to the 1S0 → 3P1 of Bi3+. Both the excitation bands induce efficient energy transfer to the excited states of Eu3+. In both the cases, the energy transfer efficiency can reach upto ~97%. The energy transfer from the sensitizer (Bi3+) to the activator (Eu3+) occurs mainly through dipole-dipole interactions. The occurrence of energy transfer from Bi3+ to the Eu3+ is corroborated from both the steady state and decay lifetime studies. Color saturation of the red emission when excited in the wavelength range ~330–380 nm is observed ~70–85%. CIE chromaticity reveals the tunability of the color emission by changing the activator concentration.

Anomalous structural transformations of Gd-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=- nanopowders obtained in the combustion mode by the glycine-nitrate method

The structural states of Gd2O3 and Gd2O3 : 2% Eu3+ synthesized by the glycine-nitrate method were studied. As a result of this synthesis, in addition to the known cubic modification of gadolinium oxide, two new previously unknown phases are formed. The first phase is formed during prolonged exposure at room temperature of the initial nanocrystalline cubic structure obtained at a synthesis temperature of 650oC. The second phase has orthorhombic syngony and is formed during either long-term synthesis at a temperature of 650oC, or short-term syntheses at a higher temperature. Both phases pass into the traditional cubic modification during further high-temperature annealing. In addition, the effect of structural &amp;quot;infection&amp;quot; was found, which consists in the fact that during annealing of the cubic phase of Gd2O3 doped with Eu3+ ions in the range of 800-1100oC, its partial transition into the monoclinic phase occurs, which disappears with a further increase in the annealing temperature. Keywords: synthesis of Gd2O3, glycine-nitrate method, nanocrystalline state, X-ray diffraction research methods, phase transitions.

Well-defined Gd(OH)CO3, Gd2O(CO3)2·H2O, and Gd2O3 compounds with multiform morphologies and adjustable particle sizes: Synthesis, formation process, and luminescence properties

A variety of monodisperse size-tunable Gd(OH)CO3 nanospheres and Gd2O(CO3)2·H2O microplates have been synthesized via a facile homogeneous precipitation route with a mixing solvent of isopropanol (IPA) and H2O. The morphology and particle size of the gadolinium compounds can be tuned in a controlled manner by simply adjusting the volume ratio of IPA/H2O in solvent or reaction temperature and time. Both the amorphous Gd(OH)CO3 nanospheres and crystalline Gd2O(CO3)2·H2O microplates have been transformed into cubic phase of Gd2O3 after a calcination process in air. Interestingly, the Gd2O3 products perfectly inherit the well-defined morphology, good unifomity and dispersity of the precursor samples except for a shrinkage in particle size due to crystallization and coalescence at high temperature. The Gd2O3:Eu3+ and Gd2O(CO3)2·H2O:Tb3+ samples show red and green emission colors under ultraviolet excitation, and Gd2O3:Yb,Ln3+ (Ln = Er and Ho) samples exhibit characteristic orange-red and green emissions when excited at near-infrared (NIR) excitation. The morphology- and particle size-dependent luminescence performances of phosphors are studied in detail. Moreover, the light emitting diode (LED) devices fabricated with the corresponding down-conversion or up-conversion phosphors can display dazzling characteristic multicolor emissions, revealing that the as-synthesized luminescent materials have potential application prospect in the fields of LEDs, light display systems, and optoelectronic devices.

Interaction between gadolinium zirconate and LiCl–Li2O melt

The interaction between Gd2Zr2O7 and molten LiCl–Li2O (2 wt%) was studied for 24–52 h at 650–710 °C in an argon atmosphere. Gd2Zr2O7 is analyzed as a promising structural material for sensors used during pyrochemical reprocessing of spent nuclear fuel and for long-term storage or final disposal of high-level nuclear wastes.The chemical stability of Gd2Zr2O7 relative to the components of the LiCl–Li2O melt was thermodynamically evaluated. The surface morphology and structure of the samples before and after the experiment were analyzed using an X-ray diffractometer and scanning electron microscopy. The formation of a new Li+-doped phase based on Gd2Zr2O7 and the Gd2O3 evolution onto the material surface was revealed by the X-ray diffraction analysis (XRD). Changes in the microstructure of the samples confirm the presence of large particles in the surface layer corresponding to the Gd2O3 phase, which is in good agreement with the XRD data. A profilometer was used to measure the roughness of the ceramics. Presumably, the thickness of the lithium-doped Gd2Zr2O7 film, which is inhomogeneously distributed over the surface of the samples, was 3 μm. Therefore, it was found that dense Gd2Zr2O7 (F) and Gd2Zr2O7 (P) ceramics can be used in LiCl–Li2O (2 wt %) as a structural material resistant to the high-temperature chemical attack.

IR-transparent MgO-Gd2O3 composite ceramics produced by self-propagating high-temperature synthesis and spark plasma sintering

A glycine-nitrate self-propagating high-temperature synthesis (SHS) was developed to produce composite MgO-Gd2O3 nanopowders. The X-ray powder diffraction (XRD) analysis confirmed the SHS-product consists of cubic MgO and Gd2O3 phases with nanometer crystallite size and retains this structure after annealing at temperatures up to 1200 °C. Near full dense high IR-transparent composite ceramics were fabricated by spark plasma sintering (SPS) at 1140 °C and 60 MPa. The in-line transmittance of 1 mm thick MgO-Gd2O3 ceramics exceeded 70% in the range of 4–5 mm and reached a maximum of 77% at a wavelength of 5.3 mm. The measured microhardness HV0.5 of the MgO-Gd2O3 ceramics is 9.5±0.4 GPa, while the fracture toughness (KIC) amounted to 2.0±0.5 MPa·m1/2. These characteristics demonstrate that obtained composite MgO-Gd2O3 ceramic is a promising material for protective infra-red (IR) windows.

Synthesis and study of nanosized gadolinium oxide modified by zirconium oxide

A method for the fabrication of nanosystems Gd2O3, 90%Gd2O3–10%ZrO2, 80%Gd2O3–20%ZrO2, 70%Gd2O3–30%ZrO2 from salt solutions using freeze-drying is studied. Using the TEM method, the particle sizes (18–40 nm) after annealing at 700 оС are estimated. In the Gd2O3–ZrO2 system the phases of Gd2O3 and Gd2Zr2O7 are present. The acid-base properties of the surface are evaluated using the Hammett indicator method: there are Brønsted acid sites with pKa = 1.7; 2.1; 3.46; 5.2 and the Brønsted base site with pKa = 7.4. The addition of zirconium oxide to gadolinium oxide sharply increases the value of specific adsorption and donor surface properties. Using DSC method, the process of acid-base catalysis as exemplified by thermodestruction of activated carbon in the presence of the systems Gd2O3, Gd2O3–ZrO2 is assessed. Decomposition of activated carbon in the presence of Gd2O3, 90%Gd2O3–10%ZrO2, 80% Gd2O3 -20%ZrO2, and 70%Gd2O3–30%ZrO2 proceeds faster. The activation energy of the processes decreases from 1.67 to 0.56 kJ/mol, while the thermal effect and mass loss increase.

Unraveling the electronic structures in different phases of gadolinium sesquioxides performed by electron energy loss spectroscopy

The gadolinium sesquioxide (Gd2O3) with its bandgap of ∼5.4 eV and high dielectric permittivity and refractive index has been used widely in optics, magnetic resonance imaging, and high k dielectrics. Electron energy loss spectroscopy (EELS) reveals spectral features at 13.5 eV and 15 eV, which can be interpreted as surface and volume plasmons, respectively. The unusual surface exciton polariton, with surface resonances associated with excitonic onsets, was also observed at ∼7.5 eV. Because of the differences in electronic structures between the cubic and the monoclinic phases of Gd2O3, it is straightforward to distinguish the two phases using the low-loss regime and O K-edge as a fingerprint. We further successfully performed EELS and electron diffraction to identify the crystalline phase of a single-crystal Gd2O3 film epitaxially grown on a Si(111) substrate.

Facile synthesis and characterization of novel Gd2O3–CdO binary mixed oxide nanocomposites of highly photocatalytic activity for wastewater remediation under solar illumination

In this study, pure cadmium oxide (CdO) nanoparticles and mixed gadolinium oxide (Gd2O3)–CdO nanocomposites with different Gd2O3 contents (0–15%) were synthesized by a facile precipitation technique followed by calcined treatment. The X-ray diffraction analysis illustrated that all samples had high cubic-phase purity and a good crystallinity. Further support for the formation of highly pure CdO and Gd2O3 phases was obtained via infrared spectroscopy. The morphologies of pure CdO and mixed Gd2O3–CdO nanoparticles were probed by scanning electron and transmission electron microscopy, which demonstrated that the collected samples consisted of individual semi-spherical shaped entities of different particle sizes (23–31 nm). The optical band gap of the developed samples was computed based on the Tauc equation and showed a decrease from 3.41 to 2.75 eV upon increasing the Gd2O3 content. The 3D fluorescence analysis showed that the quenching in the emission peak intensity with increasing Gd2O3 content was due to the high separation efficiency of photogenerated electron–hole pairs. Moreover, the Gd2O3(15%)–CdO nanocomposite showed superior photodegradation efficiency (89.1%) of methylene blue compared to 44.4% for pure CdO. At pH 11.5, >3-fold enhancement in degradation rate (0.044 min −1) was obtained compared to natural pH 9.6. Reusability study showed stability of the Gd2O3–CdO photocatalyst in four cycles of methylene blue degradation. Trapping experiment of holes and electrons revealed extensive contribution of holes rather than electrons in producing active oxidizing species.

Tunable multicolor emission and energy transfer of cylindrical Gd2O3:Dy3+, Tb3+, Eu3+ particles

Gd2O3:Dy3+, Tb3+, Eu3+ polychromatic luminescence phosphors with novel cylindrical morphology were successfully prepared by means of solvothermal method and subsequent calcination process. XRD results showed that the samples were all cubic Gd2O3 phase, and the introduction of rare earth dopant did not change the crystal structure of Gd2O3. FE-SEM results showed that the samples were all cylinder with slightly rough surface after calcination, and the main shape remained unchanged. Through PL, it is proved that there exists Dy3+→Tb3+ and Tb3+→Eu3+ energy transfer in Dy3+, Tb3+ co-doped Gd2O3 and Tb3+, Eu3+ co-doped Gd2O3, respectively. In addition, dipole-dipole interaction is the main interaction mode in the two systems. The tunable multicolor luminescence of Gd2O3:Dy3+, Tb3+, Eu3+ was achieved by altering the type of doped ions, increasing the amount of doped ions and changing the excitation wavelength, which has a great application prospect in the field of full-color display.

Preparation and Characterization of Nanocrystalline Gadolinium Oxide Powders and Films

Due to its magnetic, electrical, absorption, and emission properties, nanoscale gadolinium oxide is widely used in various fields. In this research, nanocrystalline Gd2O3 powders and films on glass substrates have been produced by the extraction-pyrolytic method. X-ray diffraction analysis revealed the formation of single phase Gd2O3 with cubic crystal structure and the mean crystallite size from 9 to 25 nm in all produced materials. The morphology of samples has been characterized by scanning electron microscopy and transmission electron microscopy.