A study of ZnGa2O4 phosphor prepared by the solid method

In this study, the mixtures of ZnO and Ga2O3 powder with addition of LiCl f lux were fired, the raw material mixing ratio, doping with Mn2+ and firing atmosphere effects on phosphor characteristics were investigated. When fire d 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 ai r, exhibits two new emission bands with peaks at 506 nm (Mn2+ emission cent re) and 666 nm (Mn4+ emission centre). However, if fired under vacuum, the emission spectrum presents only the 506 nm peak with increased intensity. T he 666 nm emission peak derived from a little Mn-2 oxidized to Mn4+ which s ubstituted 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 t he zinc sites. The luminescent band was associated to the spin-forbidden tr ansition, T-4(1)(4G) --> (6)A(1) (6S). (C) 1998 Kluwer Academic Publishers.