Structure and luminescent properties of Co super(2+)/Cr super(3+) co-doped ZnGa sub(2)O sub(4) nanoparticles

• Published in: Journal of luminescence 2014-09, Vol.153, p.361-368
• Main Authors: Duan, Xiulan, Liu, Jian, Wu, Yuanchun, Yu, Fapeng, Wang, Xinqiang
• Format: Article
• Language: English
• Subjects: Annealing; Chromium; Emission; Energy transfer; Inversions; Nanoparticles; X-ray photoelectron spectroscopy; X-rays
• ISSN: 0022-2313
• DOI: 10.1016/j.jlumin.2014.03.027

Co super(2+)/Cr super(3+) co-doped ZnGa sub(2)O sub(4) nanoparticles were prepared by a citrate sol-gel method. Their structure and luminescent properties were studied by using X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and fluorescence spectrophotometer. The nanoparticles with the size of 18-50 nm were obtained when the precursor was annealed at 500 degree C or above. Ga super(3+) ions occupied the octahedral sites as well as the tetrahedral sites, while Cr super(3+) ions only entered the octahedral sites by replacing Ga super(3+). The as-synthesized samples had partially inverted spinel structure and the inversion degree slightly decreased with increasing temperature. The Cr super(3+):ZnGa sub(2)O sub(4) sample exhibited an intense emission at 695 nm, corresponding to the super(2)E arrow right super(4)A sub(2) transition of octahedral Cr super(3+). The emission intensity of Cr super(3+) was largely reduced when the sample was co-doped with Co super(2+). However, the emission intensity of Co super(2+) in 2% Co/1% Cr co-doped ZnGa sub(2)O sub(4) is improved approximately 2 times when compared with 2% co-doped sample. This enhanced emission could be attributed to an efficient energy transfer from Cr super(3+) to Co super(2+). The energy transfer mechanism is also discussed.