Influence of Cr and Mn co-doping on the microstructure and optical properties of spinel structured Zn0.95−xCr0.05MnxAl2O4 nanoparticles

Cr and Mn co-doped Zn0.95−xCr0.05MnxAl2O4 nanoparticles with different contents of Mn were synthesized via simple hydrothermal route and heat treatment technology. The influences of Cr and Mn doping on the microstructure, morphology, binding energy and optical property of the as-synthesized samples were characterized. X-ray diffraction confirm that Zn0.95−xCr0.05MnxAl2O4 nanoparticles exhibit cubic spinel structure, the average crystallite size decrease and the lattice parameter increase with the increase of Mn doping concentration. X-ray energy dispersive spectroscopy and X-ray photoemission spectroscopy demonstrate Cr and Mn ions are successfully substituted for the lattice site of Zn2+, enter ZnAl2O4 matrix and mainly occupy the tetrahedral sites of the doped samples. Scanning electron microscopy and high-resolution transmission electron microscopy show the morphology of the samples are irregular spherical or ellipsoid particles with small particle size and good dispersion. Ultraviolet–visible spectra indicate co-doped samples possess strong visible light absorption ability, and the band gap decrease as Mn ions concentration increase and occur red shift. Photoluminescence spectra show the intensity decrease and occur luminescence quenching phenomenon for doped samples. The intensity of Fourier transform infrared spectroscopy for doped samples decrease slowly and occur red shift.