ZnGa2O4:Mn2+ nanophosphors were synthesized from zinc acetate dihydrate, gallium acetylacetonate, and manganese(II) acetate tetrahydrate in 1,4-butanediol by glycothermal method at 300 degrees C for 2 h. Their average particle diameter was 12.1 +/- 2.5 nm. We investigated the influence of temperatures of postheat-treatment in Ar on the luminescent and structural properties. The photoluminescence (PL) intensity slightly decreased after heating below 900 degrees C. The PL intensity increased between 900 and 1200 degrees C, reached at the maximum at 1200 degrees C and decreased over 1200 degrees C. The decrease of the PL intensity by heating below 900 degrees C occurred by the removal of adsorbed organic species. The X-ray diffraction profile indicated the decomposition of ZnGa2O4 to Ga2O3 and ZnO by heating over 1200 degrees C, resulting in the decrease of the PL intensity. The change in the integrated intensity of electron paramagnetic resonance due to paramagnetic Mn2+ with the temperature of heat-treatment in Ar was similar to that of the PL intensity. This suggests that the PL intensity is correlated to the incorporated Mn2+ amount. (c) 2007 The Electrochemical Society.