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Evolution of microstructures and optical properties of gadolinium oxide with oxygen flow rate and annealing temperature
摘要： In this study, the effects of oxygen flow rate and annealing temperature on Gd2O3 structures and optical properties were systematically analyzed. Gd2O3 films were deposited on both quartz and ZnS substrates by magnetron sputtering and then annealed under vacuum at 700, 800, and 900 (cid:1). Restructure and phase transformation from cubic to monoclinic occur at different temperatures depending on the oxygen flow rate. The optical band gap, which is more sensitive to the annealing temperature than oxygen flow rate changes from 5.32 to 5.65 eV. The refractive index is approximately 1.75 at 550 nm and is adjustable by the oxygen flow rate. The transmittance of the ZnS substrate with Gd2O3 film exceeds 80% and reaches 82% at the 7.5–9.5 μm range. When ZnS is coated on both sides, the transmittance is increased to approximately 90%. Our results indicate that Gd2O3 films are promising new candidates for anti-reflective coatings in the infrared region.
关键词： Rare earths,Infrared materials,Structures,Optical properties,Gadolinium oxide,Magnetron sputtering
更新于2025-09-23 15:23:52
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Ammonium oxalate-assisted synthesis of Gd2O3 nanopowders
摘要： The impacts of co-precipitation reaction temperature and duration, as well as calcination temperature and duration, on the particle morphology and properties of gadolinia (Gd2O3) nanopowders were investigated. Thermogravimetric curve of thermally treated gadolinium oxalate (Gd2(C2O4)3) showed that pure stable cubic phase Gd2O3 nanopowders could be obtained by calcining at 640 °C and higher. This finding was also supported by results obtained from Fourier Transform Infrared Spectrometry (FTIR) and Raman spectrometry. This study also shows that uniform spherules of Gd2O3 nanopowders could be obtained under controlled synthesis conditions. However, with an increase in both the co-precipitation reaction temperature and duration, the extent of agglomeration of Gd2O3 nanopowders increased, as observed under a Field Emission Scanning Electron Microscope (FESEM). The FESEM images and X-ray Diffraction (XRD) patterns also revealed accelerated grain growth and increased average crystallite size at high calcination temperatures and holding times. It was determined that the most favourable Gd2O3 particle morphology was achieved when Gd2(C2O4)3 was co-precipitated at 40 °C, then thermally degraded at 650°C, for 1 h and 4 h, respectively. Estimated Scherrer’s average crystallite size of the resulting Gd2O3 nanopowders was 16.54 nm, which was further affirmed with the transmission electron microscope (TEM) image, where crystallite sizes of 3 to 27.5 nm were observed in the Gd2O3 sample. This specimen also demonstrated a considerably large specific surface area of 9.16 m2/g, as measured using a Brunauer–Emmett–Teller (BET) analyser.
关键词： Ammonium oxalate,Gadolinium oxide,Nanopowders,Co-precipitation,Gadolinia
更新于2025-09-19 17:15:36
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Intrinsic Defect-Assisted UV-Visible Energy Conversion in Gd <sub/>2</sub> O <sub/>3</sub> :Er Nanoparticles
摘要： The correlations between defectiveness and optical properties of Er-doped Gd2O3 nanoparticles coupled into cubic and monoclinic crystal structures were studied employing XPS and PL spectroscopies. The main focus of this research is paid to the cubic Gd2O3 phase, which is more suitable for light-emitting purposes. It is shown that oxygen-related point defects are the precursors for the formation of cationic irregulars – “defective” Gd3+ ions with local energy levels in the energy band gap of Gd2O3. Energy transfer from Gd3+ intrinsic defects to Er3+ dopants provides an additional channel for UV–visible radiation conversion. These Er3+ ions have bimodal distribution due to the non-equivalent lattice sites of “defective” Gd3+ ions. An increase of Er3+ concentration leads to the giant phonon softening effect, which opens up a new prospective way to enhance energy conversion efficiency.
关键词： UV conversion,photoluminescence,gadolinium oxide,erbium,defects
更新于2025-09-19 17:15:36
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Mesoporous silica modified luminescent Gd2O3:Eu nanoparticles: physicochemical and luminescence properties
摘要： Highly colloidal Gd2O3:Eu nanoparticles (core-NPs) were synthesized by thermal decomposition via weak base at low temperature. The sol–gel chemical process was employed for silica layer surface coating to increase solubility, colloidal stability, biocompatibility, and non-toxicity at the ambient conditions. XRD results indicate the highly puri?ed, crystalline, single phase, and cubic phase Gd2O3 nanocrystals. TEM image shows that the mesoporous thick silica layer was effectively coated on the core nanocrystals, which have irregular size with nearly spherical shape and grain size about 10–30 nm. An absorption spectra and zeta potential results in aqueous media revealed that solubility, colloidal stability, and biocompatibility character were enhanced from core to core–shell structure because of silica layer surface encapsulation. The samples, demonstrated excellent photoluminescence properties (dominant emission 5D0 → 7F2 transition in the red region at 610 nm), indicated to be used in optical bio-detection, bio-labeling, etc. The photoluminescence intensity of the silica shell modi?ed core/shell NPs was suppressed relatively core-NPs; it indicates the multi-photon relaxation pathways arising from the surface coated high vibrational energy molecules of the silanol groups. The core/nSiO2/mSiO2 nanocrystals display strong emission (5D0 → 7F2) transition along with excellent solubility and biocompatibility, which may ?nd promising applications in the photonic based biomedical ?eld.
关键词： silica,Gadolinium oxide,Biocompatible,Luminescence properties,Zeta potential,Mesoporous
更新于2025-09-09 09:28:46