Optical response of Eu3+-activated MgAl2O4 nanophosphors for Red emissive

• Published in: Journal of materials science. Materials in electronics 2023-04, Vol.34 (11), p.955, Article 955
• Main Authors: Rao, B. Nageswara, Rao, P. Tirupathi, Basha, Sk. Esub, Prasanna, D. S. L., Samatha, K., Ramachandra, R. K.
• Format: Article
• Language: English
• Subjects: Absorption spectroscopy; Characterization and Evaluation of Materials; Chemistry and Materials Science; Chromaticity; Crystallites; Crystallization; Decomposition; Diffraction patterns; Emission analysis; Energy gap; Energy levels; Europium; Functional groups; High resolution electron microscopy; Luminescence; Magnesium aluminate; Materials Science; Nanoparticles; Nanophosphors; Optical and Electronic Materials; Phosphors; Photoluminescence; Room temperature; Spectrum analysis; Temperature dependence; X ray powder diffraction; X ray spectra
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-023-10341-w

Eu 3+ -activated magnesium aluminate phosphors were successfully synthesized by nitrate–citrate gel combustion method and thermally treated at 650, 750, 850, and 950 o C. The powder X-ray diffraction pattern showed that all MgAl 2 O 4 : x Eu 3+ (0 ≤  x ≤  0.10) samples exhibit crystallized cubic phase of spinel structure with space group Fd-3 m. The Debye–Scherrer equation is used to estimate average crystallite size values and are found to be 8.5–12.1 nm, that are also confirmed by high-resolution transmission electron microscopy (HRTEM) images. TGA–DTG results suggest that the maximum decomposition of the precursors were observed below 600 o C. Accordingly, the decomposition temperature was taken 650 o C and above. The functional groups of the powder samples were determined by FTIR. Energy levels were characterized, and the band gap energy ( E g ) has been calculated using UV–Vis absorption spectroscopy and found to be in the range of 5.08–5.19 eV. The FESEM images shows that the nanoparticles are agglomerated and are in nonuniform spherical shape with reduced average particle size from 27 ± 4.1 to 24.1 ± 3.3 nm. Further, the elemental composition of the as-prepared samples was analyzed by using energy-dispersive X-ray spectra (EDAX). The photoluminescent property of MgAl 2 O 4 : x Eu 3+ samples was investigated using room-temperature emission spectroscopy. These phosphors show different emissions of Eu 3+ corresponding to 5 D 0 → 7 F J =1,2,3,4 transitions which lie in the wavelength range from 590 to 703 nm. The red emission transition 5 D 0 → 7 F 2 (∆ J  = 2) centered at 612 nm has been known to be hypersensitive, strong, and more intense of all samples. The PL emission intensity increases up to 4 mol% Eu 3+ concentration and then decreases due to the process of concentration quenching. The chromaticity color coordinates were obtained from the luminescence emission spectrum. The temperature-dependent luminescence property of MgAl 2 O 4 :4%Eu 3+ phosphor has also been discussed. These results showed that MgAl 2 O 4 : x Eu 3+ could be a prominent material for the production of artificial red light in red LEDs.