Eu2+-doped beta -aluminas (Sr1-xBaxMgAl10O17:Eu-0.01(2+), 0 less than or equal to x less than or equal to 1) Were successfully synthesized by direct solid-phase reaction. Contrary to other p-aluminas, Srp-alumina doped with Eu2+ (SrMgAl10O17: Eu2+) showed two strong phosphorescent peaks at 482 and 502 nm, which were different from the peal, of fluorescence (465 nm). These phosphorescent peaks were dependent on the excitation wavelength. The peak at 482 nm was observed after removal of the excitation at a short wavelength below 254 nm, whereas the peak at 502 nm was seen after removal of the excitation at a wavelength between 304 and 365 nm. The afterglow curves also showed different decay behaviors after removal of the light excitation at those different wavelengths. A model has been proposed which indicates that three sites can be occupied by Eu2+ ions in SrMgAl10O17, whereas there is only a single site in BaMgAl10O17.