A study of ZnGa2O4 phosphor prepared by the solid method

In this study, the mixtures of ZnO and Ga2O3 powder with addition of LiCl flux were fired, the raw material mixing ratio, doping with Mn2+ and firing atmosphere effects on phosphor characteristics were investigated. When fired at 1200 degrees C, its phosphor powder emits a broad-band spectrum range between 375 nm to 700 nm, with a peak at 470 nm. The optimal composition of phosphors is about ZnO/Ga2O5 = 47/53. Manganese-doped ZnGa2O4, fired in air, exhibits two new emission bands with peaks at 506 nm (Mn2+ emission centre) and 666 nm (Mn4+ emission centre). However, if fired under vacuum, the emission spectrum presents only the 506 nm peak with increased intensity. The 666 nm emission peak derived from a little Mn-2 oxidized to Mn4+ which substituted Ga3+ to occupy the B sites of the spinel structure. The emission intensity of the 506 nm peak of Zn1-xMnxGa2O4 is strongest when [Mn2+] x = 0.006 and decreases markedly as the concentration of Mn2+ exceeds x = 0.01. Most of the substitutional Mn2+ doping species in spinel ZnGa2O4 occupy the zinc sites. The luminescent band was associated to the spin-forbidden transition, T-4(1)(4G) --> (6)A(1) (6S). (C) 1998 Kluwer Academic Publishers.