Synthesis and optical properties of ZnAl2O4/Al2O3 - Cr3+ composite materials
Zinc aluminate - alumina (ZnAl2O4/Al2O3) systems doped with Cr3+ different concentrations were synthesized by sol-gel method. The samples were characterized by X-ray diffraction (XRD), photoluminescence (PL) and photoluminescence excitation (PLE) spectra. The results showed that Cr3+ dopant concentration had a significant effect on the lattice constants of ZnAl2O4/Al2O3 composite and their luminescence characteristics. When increasing Cr3+ contents, the lattice constants of both the ZnAl2O4 and α-Al2O3 crystals increase. For the samples with low Cr3+ dopant concentrations, the PL spectra mainly consist of sharp lines assigned to the 2E(2G)→4A2(4F) transitions of Cr3+ ions located in strong octahedral field of the ZnAl2O4 and α-Al2O3 crystals. With increasing Cr3+ concentration, in the PL spectra appears very broad emission band in the long-wavelength side, which originates from the 4T2(4F)→4A2(4F) transitions within the Cr3+ ions located in the weak octahedral sites of the ZnAl2O4 and α-Al2O3 crystals.
