Luminescent-Efficiency Improvement by Alkaline-Earth Fluorides Partially Replacing MgO in 3.5MgO⋅0.5MgF[sub 2]⋅GeO[sub 2]:Mn[sup 4+] Deep-Red Phosphors for Light Emitting Diodes

We have investigated the luminescent properties of partially replaced by alkaline-earth fluorides under near-UV and blue light excitations. The alkaline-earth fluoride other than probably acts as a flux. The sample with the replacement of of MgO by of , i.e., (MGF-SF08), shows efficient deep-red emission at , and its photoluminescence (PL) intensity is over 3 times higher than a commercial (YAG) phosphor, P46-Y3, under light excitation. Under light excitation, MGF-SF08 is over 7 times higher than a commercial (YOS) phosphor, P22-RE3, in PL peak intensity. Moreover, the alkaline-earth fluorogermanate phosphors show more thermal stability than the YAG and the YOS phosphors in integrated PL intensity. The integrated PL intensity of MGF-SF08 at is still 95% of that measured at room temperature under light excitation. These results imply that -doped alkaline-earth fluorogermanates are promising candidates of deep-red phosphors for near-UV and blue light emitting diodes.