Photoluminescence Properties of BaMgAl10O17 Doped with High Concentration of Mn2+ for Blue-LED-Based Solid-State Lighting

In most of host crystals, the 3d-3d Mn2+ transition from the 6A1 (6S) ground state to the 4T2 (4G) excited state is located at the blue-light region. This transition is both parity- and spin-forbidden. Phosphors doped with high concentration of Mn2+ without causing serious concentration quenching can be expected to have high absorption efficiency for the excitation light, and consequently, high photoluminescence (PL) output. As an example of such phosphors, we have investigated PL properties of BaMgAl10O17 (BAM) doped with Mn2+ for excitation by blue light-emitting diodes (LEDs). The PL peak intensity reaches its maximum at Mn = 0.45 mol/mol substituting for Mg sites. The BaMg0.55Mn0.45Al10O17 (BAM-Mn045) phosphor shows pure green emission centered at 517 nm, and its PL intensity is about 1.25 times higher than a commercial yellow (Y, Gd)3(Al, Ga)5O12:Ce3+ (YAG) phosphor, P46-Y3, under 450 nm light excitation. The internal quantum efficiency of the BAM-Mn045 phosphor under 450 nm light excitation is 60%. Moreover, the BAM-Mn045 phosphor exhibits less thermal quenching than P46-Y3 in PL integrated intensity. The integrated PL intensity of the BAM-Mn045 phosphor at 150°C is still over 80% of that measured at room temperature under 405 nm light excitation.