Photoluminescence Property of Eu3+ doped CaSiO3 Nano-phosphor with Controlled Grain Size

Multicolor tunable bright photoluminescence in Ca2+/Mg2+ modified Eu3+ doped ZnGa2O4 phosphors under UV excitation for solid state lighting applications

The Eu³⁺ doped and Mg²⁺/Ca²⁺ co-doped ZnGa₂O₄ phosphor samples were synthesized by solid-state reaction method and their structural and optical properties studied. The phase, crystallinity and particles size of the phosphor samples were studied by XRD and SEM measurements. EDS analyses were used to identify the elements present in the phosphor materials. The vibrational groups present in the phosphor samples were examined by Fourier transform infrared (FTIR) measurements. Pure ZnGa₂O₄ emits intense blue light under 260 nm excitation. However, Eu³⁺ doped and Mg²⁺/Ca²⁺ co-doped ZnGa₂O₄ phosphor samples exhibit intense red emission under 393 nm excitation. A bluish white color is observed in these samples under 290 nm excitation. The maximum PL emission intensity is found at 0.1 mol% Eu³⁺ doping concentration. For higher concentrations, concentration quenching was observed due to dipole-dipole interaction. The emission intensity is enhanced upto 1.20 and 2.91 times on co-doping of Mg²⁺ and Ca²⁺via induced crystal field due to charge imbalance. The emission intensity of the phosphor is found to enhance further on annealing the samples at 873 K. Under various excitation wavelengths, color tunability was seen from blue to bluish-white to red regions. The lifetime of the ⁵D₀ level of the Eu³⁺ ion improves via doping of Mg²⁺/Ca²⁺ ions and it increases appreciably on annealing. The temperature dependent photoluminescence study (TDPL) reveals a thermal quenching behavior of the sample with thermal stability ∼65% and activation energy ∼0.223 eV in the Eu³⁺/Ca²⁺ co-doped ZnGa₂O₄ phosphor sample.

Tailoring the Emission Behavior of WO3 Thin Films by Eu3+ Ions for Light-Emitting Applications

The article reports the successful fabrication of Eu³⁺-doped WO₃ thin films via the radio-frequency magnetron sputtering (RFMS) technique. To our knowledge, this is the first study showing the tunable visible emission (blue to bluish red) from a WO₃:Eu³⁺ thin film system using RFMS. X-ray diffractograms revealed that the crystalline nature of these thin films increased upto 3 wt% of the Eu³⁺ concentration. The diffraction peaks in the crystalline films are matched well with the monoclinic crystalline phase of WO₃, but for all the films', micro-Raman spectra detected bands related to WO₃ monoclinic phase. Vibrational and surface studies reveal the amorphous/semi-crystalline behavior of the 10 wt% Eu³⁺-doped sample. Valence state determination shows the trivalent state of Eu ions in doped films. In the 400-900 nm regions, the fabricated thin films show an average optical transparency of ~51-85%. Moreover, the band gap energy gradually reduces from 2.95 to 2.49 eV, with an enhancement of the Eu³⁺-doping content. The doped films, except the one at a higher doping concentration (10 wt%), show unique emissions of Eu³⁺ ions, besides the band edge emission of WO₃. With an enhancement of the Eu³⁺ content, the concentration quenching process of the Eu³⁺ ions' emission intensities is visible. The variation in CIE chromaticity coordinates suggest that the overall emission color can be altered from blue to bluish red by changing the Eu³⁺ ion concentration.