Luminescence Properties of Gd2(MoO4)3 Modified with Sm(III) and Tb(III) for Potential LED Applications

Abstract

Light-emitting phosphors, doped with lanthanide ions of Tb(III) and Sm(III) of the type Gd1.97-y SmyTb0.03(MoO4)3 (y = 0.01–0.11, step 0.02) and Gd1.95-xSm0.05Tbx(MoO4)3 (x = 0.01–0.09, step 0.02), were synthesized and characterized by X-ray diffraction, UV-Vis spectroscopy, scanning and transmitting electron microscopy (SEM, TEM) as well as photoluminescence spectroscopy. The effect of the doping content of Tb/Sm was followed. The unit cell parameters for Gd1.97-ySmyTb0.03(MoO4)3 and Gd1.95-xSm0.05Tbx(MoO4)3 changed with the increase in the Tb/Sm content. The microstrain values also increased, proposing an increased concentration of defects. The mean particle size was estimated to be approximately 0.6 µm. Based on a Williamson–Hall plot, the size of the crystallites was determined to be in the range of 42–60 nm for modified and pure Gd2(MoO4)3 samples, respectively. The samples excited at 406 nm exhibited characteristic emission lines of Sm (485, 555, 646 nm). The host material Gd2(MoO4)3 emission in visible light was explained by the crystal structure defects, namely, oxygen vacancies. The CIE x/y color coordinates of the phosphors were determined and the related points were located in the green-yellow/pale yellow region of the visible light. The excited state lifetimes were determined for both groups of the samples, showing values in the millisecond range and indicating the samples as promising phosphors.

Constructing Direct Z-Scheme Y2TmSbO7/GdYBiNbO7 Heterojunction Photocatalyst with Enhanced Photocatalytic Degradation of Acetochlor under Visible Light Irradiation

“…The XRD spectrum of YGHP includes all the peak and crystal surface indices found in the XRD spectra of Y2TmSbO7 and GdYBiNbO7, providing strong evidence for the successful synthesis of YGHP. To validate the crystallographic architecture, the X-ray diffraction data of Y2TmSbO7 and GdYBiNbO7 underwent Rietveld refinement using the Materials Studio program, as depicted in Figure 2a and Figure 3a, respectively [43]. The refinement outcomes for Y2TmSbO7 and GdYBiNbO7 yielded deviations of 5.11% and 4.01%, respectively, indicating an obvious concurrence between experimental and theoretical strengths [43], thereby validating the pyrochlore-type crystalline architecture of Y2TmSbO7 and GdYBiNbO7.…”

“…To validate the crystallographic architecture, the X-ray diffraction data of Y2TmSbO7 and GdYBiNbO7 underwent Rietveld refinement using the Materials Studio program, as depicted in Figure 2a and Figure 3a, respectively [43]. The refinement outcomes for Y2TmSbO7 and GdYBiNbO7 yielded deviations of 5.11% and 4.01%, respectively, indicating an obvious concurrence between experimental and theoretical strengths [43], thereby validating the pyrochlore-type crystalline architecture of Y2TmSbO7 and GdYBiNbO7. Meanwhile, both compounds crystallize in the cubic crystallographic system with a space group of Fd3m, demonstrating single-phase behavior.…”

Extrinsic Oxygen Vacancies Formation during Crystallization of Al2W3O12 by Calcination in Air

“…DRS spectra of the calcined Al 2 W 3 O 12 powders, especially at lower temperatures (from 500 to 570 °C), Figure a, suggest a higher absorption in the visible region, which can be attributed to the introduction of extrinsic point defects formed during the heat treatment in air. , The relative intensities of light absorption in the visible range gradually decrease as the calcination temperature increases, reaching at 620 °C a much lower absorption level than the one exhibited by the powder calcined at 500 °C. Therefore, the enhancement of light absorption at lower calcination temperatures can be due to a higher concentration of extrinsic oxygen vacancies (determined by EPR, vide infra ) which agrees with the color changes (Figure S1, Supporting information) and volumetric expansion (Tables S1 and S5, Supporting information) observed in these samples.…”

“…As the heat treatment temperature increases, the Al 2 W 3 O 12 powders change color from dark gray (A500) to white (A620) suggesting that the extrinsic oxygen vacancy content is decreasing. A 2 M 3 O 12 -type materials are known wide-band-gap semiconductors that do not absorb light within the visible range, ,, therefore, the color of the powders could be an indicator of the presence of point defects.…”

Light Emitting Rare Earth Doped K3GdF6:Eu3+ for Spectral Mapping/Imaging Studies

“…32,33 Due to the comparable oxidation state and almost identical ionic radii, luminous lanthanides can be easily doped into Gd 3+ host matrices. 34 Gadolinium (Gd 3+ ) ions exhibit magnetic behavior due to seven unpaired inner 4f electrons located near the nucleus and essentially shielded by the outer closed-shell electrons ( 5 S 2 and 5 P 6 ) in the crystal field. 35 Compared to other paramagnetic rare earth ions, Gd 3+ ions are chosen because of their larger magnetic moment and isotropic electronic ground state ( 8 S 7/2 ).…”