New long afterglow phosphors of Sr 4 Al 14 O 25 :Yb 2+ , Dy 3+ and SrAl x O (1+1.5 x ) :Yb 2+ (x=3, 4, 5) were prepared by sintering the thermally decomposed precursors under reducing condition at 1200–1400°C. The thermally decomposed precursors were obtained by heating either hydroxide or nitrate mixtures at temperatures below 300°C. The phosphor Sr 4 Al 14 O 25 :Yb 2+ , Dy 3+ showed long afterglow property comparable with the famous phosphor Sr 4 Al 14 O 25 :Eu 2+ , Dy 3+ in phosphorescence life time though phosphorescence intensity is weaker than the latter.