New long-afterglow phosphors: Yb2+-doped strontium aluminates

New long afterglow phosphors of Sr4Al14O25:Yb2+, Dy3+ and SrAlxO(1+1.5x):Yb2+ (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 Sr4Al14O25:Yb2+, Dy3+ showed long afterglow property comparable with the famous phosphor Sr4Al14O25:Eu2+, Dy3+ in phosphorescence life time though phosphorescence intensity is weaker than the latter.