The luminescence properties of orange-yellow-emitting Eu2+ -activated Sr3SiO5 were optimized for application to blue/near ultraviolet (n-UV) light-emitting diodes (LEDs). Sr 2.97SiO5: Eu0.03 2+ showed strong orange-yellow emission peaking at ∼580 nm under blue and n-UV light of 450 and 405 nm, respectively, and the effects of Ca and Ba substitutions into Sr2+ sites on the emission band change were investigated. For the substitution of Ca, Ca3 Si O5: Eu2+ showed no orange-yellow emission under blue light due to the different crystal structures of Ca3Si5 (monoclinic) and Sr3 Si O5 (tetragonal). The redshift and blueshift of the emission band of (Sr1-x Bax)3 Si O5: Eu2+ were explained by the competition between crystal field effect and Nephelauxetic effect. The 460 nm -emitting blue LED-pumped white LED with Sr3 SiO5: Eu2+ or a mixture of Sr3SiO5: Eu2+ and green phosphor (Ba2 SiO4: Eu2+) were fabricated and they showed color coordinates of (0.343, 0.281) and (0.349, 0.339), respectively. © 2009 The Electrochemical Society.