Lithium carbonate flux was introduced in the preparation of La(2)o(2)CO(3): Eu3+ oxycarbonate phosphor particles to improve the photoluminescence intensities. The flux treatment brought increasing in the crystallinity of oxycarbonate phosphor accompanying the phase transition from the two-phase mixture of tetragonal and monoclinic forms to single hexagonal phase of rare earth oxycarbonate, resulting in the increase of the emission intensity.