The relative emission yield and lifetime have been obtained as functions of Tb3+ concentration fur both (D4-Fj)-D-5-F-7 and D-5(3)-F-7(j) transitions in (Y1-xTbx)BO3 phosphates. The concentration quenching of the (D4-Fj)-D-5-F-7 transition was analyzed by intercenter energy migration on the basis of dipole-dipole interaction. The decay behavior of 5D3-7Fj transition, for which well-known cross relaxation has been accepted as a main cause, was analyzed by a direct quenching mechanism. On the other hand, it is most likely that this phosphor could be of practical use as a green component of plasma TV application because the relatively strong absorption arises in the vacuum ultraviolet range. The optimum Tb3+ concentration range was suggested to be 10 similar to 20 mol % when considering the problem practically.