γ-Al2O3:Ce3+Cu2+ as a phosphor material; DFT+U and experimental approach

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AbstractThe γ-Al2O3and Ce3+Cu2+-doped γ-Al2O3powders have been synthesized by sol-gel method. Phases of the synthesized powders were characterized with X-ray diffraction. Morphological analysis and elemental composition of the samples were determined by scanning electron microscopy, high-resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. Luminescence characterizations have been used to study the synthesized samples.Ab initiocalculations by the use of local density approximation with the HubbardUcorrelation were used to compute the structural, electronic and optical properties of γ-Al2O3and Al2O3:Ce3+Cu2+. The results indicate that the particle size and morphology of the samples depend on the concentration of the dopants. In comparison with undoped γ-Al2O3sample, the intensities of emission peaks at 430 and 458 nm of Ce3+Cu2+-doped γ-Al2O3powders have been enhanced. This shows that, increasing Ce3+and Cu2+concentration causes an increase in the number of emitting ions which is expected in order to increase the number of applications of γ-Al2O3:Ce3+Cu2+composite powders. The photoluminescence spectrum detected at$\lambda$ex = 253 nm shows a new peak located at 549 nm due to Cu2+ions. This was confirmed computationally when the Ce_4f and Ce_5d states are found in the conduction band while the Cu_4p state was found at conduction band minimum and Cu_3d state at valence band maximum. This location of states showed there is no possible luminescence from the Ce3+ions. The only possible luminescence was due to transition from Cu_4p to Cu_3d states.