The structural and luminescence characteristics of a sol-gel combustion synthesized Y 3 Al 5-x Ga x O 12: Bi 3+ phosphor with different concentration of Ga 3+ were investigated. The Rietveld refinement analysis and luminescence studies indicated that increasing the concentration of the Ga ions changed the bond lengths and lattice parameters of the dodecahedron bonds and as a result the Bi 3+ experienced a different anionic environment in the YAG host. A systematic shift of the photoluminescence excitation and emission spectra to higher wavelengths was observed with an increase of the Ga 3+ concentration. The shift is attributed to the distortion of the host lattice as observed from the changing parameter and the covalency of the host with an increase of the Ga 3+ concentration.