Enhanced Luminescence of Magnesium Germanate Deep Red Phosphors for LED Application

Abstract: Luminescence intensity of 3.5MgO∙0.5MgF2∙GeO2:Mn4+ was improved to 144%, 142%, and 152% by changing MgF2 to CaF2, SrF2, and BaF2, respectively. MgF2 enhances the crystalline quality of Mg28Ge10O48, the main phase of 3.5MgO∙0.5MgF2∙GeO2, by providing F ions to the structure and increasing the diffusivity for solid-state reaction. CaF2, SrF2, and BaF2 also function as fluxes, in addition to supplying F ions. Their double contributions to increasing the crystallinity were suggested as the reason of the improved luminescence. The LED lamp including 3.5MgO∙0.5SrF2∙GeO2:Mn4+ and Y3Al5O12:Ce3+ (YAG) shows stable performance for various forward current and higher color rendering index than the conventional YAG-based white LED lamp.