Аннотация:Phase relationships in the LuAl3(BO3)4-(K2Mo3O10-Lu2O3-B2O3) pseudo-quaternary system have been studied in the temperature range from 1130 to 900оС, and the results obtained for 25 wt.% LuAl3(BO3)4 (LuAB) concentration were presented graphically as their projection onto the cross-section at 900°C of a temperature-composition diagram. Li2WO4––B2O3 flux was also used for LuAB crystallization. Single crystals were grown on dipped “point” seeds. The absorption spectra of (Er,Yb):LuAB crystals were measured at room temperature. The optical and emission spectrum and lifetime of the 4I13/2 energy level were determined.