InGaN-based blue LEDs and, specifically luminescent materials, are described containing yttrium oxide, oxides of rare earth metals, as well as aluminium oxide in proportions that yield a luminescent material whose average composition fits the general formula (Y1−x−yCexΣLny)3+αAl5O12+1.5α, where α—defines increase in stoichiometric index over the known value for yttrium-gadolinium garnet and varies between 0.033 and 2; x—is atomic fraction of cerium, 0.0001-0.1; ΣLny —is one or more lanthanides from the Gd, Tb, La, Yb group, whose atomic fraction in an yttrium sub-lattice is 0.01 0.