Attractive new blue-emitting phosphors for use in low-pressure mercury gas discharge lamps are synthesized by Eu-substitution in the barium aluminum oxynitride host lattice with the beta-alumina-type structure. The emission spectra of these phosphors for 254 nm excitation show a band at about 450 nm with a shoulder at higher wavelength. The maximum quantum efficiency of these materials is about 85-90% just like commercial BaMgAl10O17:Eu: with the beta-alumina type structure. The nonoptimized oxynitride phosphors are more sensitive to oxidation (at 873 K) and to short-term depreciation due to 185 nm irradiation compared to commercial BaMgAl10O17:Eu. However, the maintenance of the oxynitride phosphors in single component fluorescent lamps is improved. Calculations indicate that by using these phosphors in tricolor fluorescent lamps instead of BaMgAl10O17:Eu with the beta-alumina type structure, the color rendering index will improve while the lumen output remains high.