Abstract: There is provided a long-lasting phosphor activated by divalent europium and having a chemical composition RO.multidot.a(Al.sub.1-x Ga.sub.x).sub.2 O.sub.3 .multidot.b(Y.sub.1-y Sc.sub.y).sub.2 O.sub.3 .multidot.cB.sub.2 O.sub.3 .multidot.dEu.sup.2+ .multidot.eM.sup.n+ (where R is at least one selected from the group consisting of alkaline-earth metals including Ba, Sr, Ca and Mg and Zn, and M is at least one auxiliary activator selected from the group consisting of Nb, Zr, Bi, Mn, Sn, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) wherein a, b, c, d, e, x and y are within ranges of:0.3.ltoreq.a.ltoreq.8,0<b.ltoreq.0.2,0.001.ltoreq.c.ltoreq.0.2,0.001.ltoreq.d.ltoreq.0.3,0.001.ltoreq.e.ltoreq.0.3,0.ltoreq.x.ltoreq.1.0, and0.ltoreq.y.ltoreq.1.0.There is also provided a long-lasting phosphor activated by divalent europium and having a chemical composition RO.multidot.a(Al.sub.1-x Ga.sub.x).sub.2 O.sub.3 .multidot.b(Si.sub.1-y Ge.sub.y)O.sub.2 .multidot.cEu.sup.2+ .multidot.dM.sup.