Novel two-phase yellow phosphors are disclosed having a peak emission intensity at wavelengths ranging from about 555 nm to about 580 nm when excited by a radiation source having a wavelength ranging from 220 nm to 530 nm. The present phosphors may be represented by the formula a[Sr.sub.x(M1).sub.1-x].sub.zSiO.sub.4.(1-a)[Sr.sub.y(M2).sub.1-y].sub.uS- iO.sub.5:Eu.sup.2+D, wherein M1 and M2 are at least one of a divalent metal such as Ba, Mg, Ca, and Zn, the values of a, x, y, z and u follow the following relationships: 0.6.ltoreq.a.ltoreq.0.85; 0.3.ltoreq.x.ltoreq.0.6; 0.85.ltoreq.y.ltoreq.1; 1.5.ltoreq.z.ltoreq.2.5; 2.6.ltoreq.u.ltoreq.3.3; and Eu and D each range from 0.001 to about 0.5. D is an anion selected from the group consisting of F, Cl, Br, S, and N, and at least some of the D anion replaces oxygen in the host silicate lattice of the phosphor. The present yellow phosphors have applications in high brightness white LED illumination systems, LCD display panels, plasma display panels, and yellow LEDs and illumination systems.