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. | VNU Journal of Science: Mathematics – Physics, Vol. 34, No. 1 (2018) 1-7 Synthesis and Optical Properties of ZnAl2O4/Al2O3:Cr3+ Composite Materials Trinh Thi Loan*, Nguyen Ngoc Long Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi, Vietnam Received 16 January 2018 Revised 02 February 2018; Accepted 15 March 2018 Abstract: 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 Cr 3+ 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 2 2 E( G)→4A2(4F) transitions of Cr3+ ions located in strong octahedral field of the ZnAl 2O4 and αAl2O3 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. Keywords: Zinc aluminate – alumina composite, sol-gel, photoluminescence. 1. Introduction Of all the materials made by man, ceramics have the longest history. Mixed metal oxides with spinel type structure are an important range of ceramic compounds with great interesting electrical, mechanical and optical properties [1]. In recent years, significant efforts have been made by several research groups on the synthesis and characterization of Cr3+ doped various host materials [2]. Because the band gaps of spinels with oxygen anions are rather wide, this circumstance allows for efficient doping with transition metal
