Photoluminescence of ZnGa2O4 phosphor prepared by a microencapsulation method

An inorganic luminescent material has been prepared using the microencapsulation method. A chemical precipitation process was used to produce a uniform ZnO layer on the surface of Ga2O3 particles. The best encapsulating effect for Ga2O3 with particle size under 5 μm, is obtained with the use of urea concentration of 0.7 M in an 0.1 M Zn(NO3)2·6H2O aqueous solution, heated at 75°C for 5–15 h. This composite powder requires a firing temperature of 1100°C and soaking time of 5 h, to synthesize phosphors with good repeatability. The synthetic ZnGa2O4 phosphor emits close to blue light at 455 nm under 254 nm excitation, and the best emission intensity is obtained when the molar ratio of ZnO/Ga2O3 approximately equals 1.0. The produced powder is anterior to the powder obtained by the traditional mechanical mixing which requires firing temperature above 1100°C with longer soaking time and emits a broad-band spectrum with a peak at 470 nm.