Effect of Alkali-Earth Metal Fluorides on Phase and Luminescence of Magnesium Germanate Phosphors

The luminescence intensity of 3.5MgO center dot 0.5MgF(2) center dot GeO(2):Mn(4+) was enhanced by 143, 141, and 149% when MgF(2) was replaced with CaF(2), SrF(2), and BaF(2), respectively. MgF(2) contributes to the enhancement of the phosphor crystallinity by inserting F(-) into the structure and by decreasing the phase formation temperature. Because CaF(2), SrF(2), and BaF(2) not only supply F(-) to the host but also function as fluxes, they can improve the crystallinity more effectively than MgF(2). A light emitting diode (LED) lamp with 3.5MgO center dot 0.5SrF(2) center dot GeO(2): Mn(4+) and Y(3)Al(5)O(12):Ce(3+) (YAG) shows a stable performance for various forward currents and higher color rendering index than that observed in a conventional YAG-based white LED lamp. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3482025] All rights reserved.