Color tunable SrZrO3:Sm3+ nanopowders with satisfactory photoluminescent, band engineering properties for warm white LEDs and advanced forensic applications

Effect of Tb3+ and Ce3+ Co-doping on the Structure and Photoluminescence Properties of Hexagonal Boron Nitride Phosphors

In the paper, we have successfully prepared hexagonal boron nitride (h-BN:Tb3+, Ce3+) phosphors with melamine as the nitrogen source. The X-ray powder diffraction patterns confirm that the sample possesses a hexagonal crystal structure within the P 6 ¯ m2 space group. It is interesting that the co-doping combination of Tb3+ and Ce3+ can markedly enhance the threshold concentration of doped activators within the limited solid solution of h-BN phosphors. Under 302 nm excitation, the h-BN:Ce3+ phosphors exhibit broadband blue light emission at 406 nm. In h-BN:Tb3+, Ce3+ phosphors, the co-doping of Ce3+ not only ensures high phase purity but also results in strong green light emission. The energy transfer efficiency from Ce3+ to Tb3+ is about 55%. The fluorescence lifetime increases with the increase of Ce3+ and Tb3+ concentration, and the fluorescence lifetime of h-BN:0.025Tb3+, 0.05Ce3+ phosphor reached 2.087 ms. Additionally, the h-BN:0.025Tb3+, 0.05Ce3+ phosphor exhibits excellent thermal performance with an activation energy value of 0.2825 eV. Moreover, the photoluminescence quantum yield of the sample exceeds 52%. Therefore, the h-BN:Tb3+, Ce3+ samples can be used as green phosphors for solid state lighting and fluorescent labeling.

Combustion Synthesis and Influence of Dy3+ ions on Structural and Photometric Attributes of Olivine-type LiMgPO4 Nanophosphors for Illumination Applications

The low-cost technique of combustion synthesis was used to synthesize the trivalent Dysprosium (Dy3+) doped olivine type Lithium Magnesium Phosphate (LiMgPO4). X-ray diffraction (XRD) analysis verified the orthorhombic phase, corresponding to the space group Pnma. The crystallite size of 50.83 nm was calculated using Debye-Scherre formula. FESEM technique was used to study the morphology of the sample which depicts its porous nature. High-Resolution Transmission Electron Microscopy (HRTEM) analysis provided an average particle size measurement of 65 ± 2.04 nm. The phosphor's photoluminescence (PL) excitation spectrum revealed distinct peaks in the ultraviolet (UV) and near-ultraviolet (near UV) regions, aligning with the characteristics of Dy3+ ions. Four emission peaks were observed in the PL spectra at various wavelengths: 4F9/2→6H15/2 (482 nm), 4F9/2→6H13/2 (578 nm), 4F9/2→6H11/2 (663 nm) and 4F9/2→6H9/2 (700 nm). Near-white light emission was observed at the Commission International de l'Eclairage (CIE) coordinates of Dy3+ activated LiMgPO4 [LMP] phosphor, which were (x = 0.41, y = 0.42) with color purity of 49.20%. The band gap of the prepared phosphor was calculated using diffuse reflectance spectra, yielding a value of 4.47 ± 0.02 eV. The results indicated that the synthesized phosphor had potential for various illumination applications when combined with other phosphors under near-UV stimulation.