A series of samples with the compositions Sr2(1-x-z/2)Eu2xLazSi1-zGazO4 were synthesized by an advanced solution method employing a water-soluble silicon (WSS) compound. It has been observed that the substitution of Si4+ by Ga3+ in charge compensated Sr2(1-x-z/2)Eu2xLazSi1-zGazO4 samples causes a phase transition from β-phase to the α-phase of Sr2SiO4 accompanied by a considerable red shift in the photoluminescence emission spectra. Internal quantum efficiencies are found to be 95% and 77% for Sr1.98Eu0.02SiO4 and Sr1.93Eu0.02La0.05Si0.95Ga0.05O4 respectively. The high quantum efficiency of the phosphors owe to the synthesis procedure as well as use of SrCl2 as flux during the heat treatment in H2/Ar atmosphere. To demonstrate its potential application, we fabricated a warm white light-emitting diode (WLED) using the Sr1.93Eu0.02La0.05Si0.95Ga0.05O4 phosphor, pumped with a 365 nm n-UV LED chip, which reflects the good color rendering index and color temperature.