A deep red-light-emitting phosphor Mn4+:CaAl4O7 for warm white LEDs

Red-light-emitting phosphors Mn4+-doped CaAl4O7 were synthesized by high temperature solid-state reaction, and we investigated their photoluminescence properties for their applications in white-light-diodes (W-LEDs). Mn4+-doped CaAl4O7 exhibited deep red emission band peaking at 635, 641 and 655 nm arising from the spin-forbidden 2E→4A2 transition of Mn4+ under near ultraviolet (UV) or blue light excitation. The Commission International de L’Eclairage (CIE) chromaticity coordinates of 0.6at.% Mn4+-doped CaAl4O7 are (0.714, 0.285) under 470 nm excitation. The electric quadrupole-quadrupole interaction was the energy transfer mechanism in Mn4+-doped CaAl4O7 phosphor, and the critical distance of energy transfer between the Mn4+ ions was estimated to be about 1.533 nm. Mn4+-doped CaAl4O7 show poor thermal quenching properties based on the temperature-dependent fluorescent spectra. Further work to improve thermal stability need be carried out for Mn4+-doped CaAl4O7 as a promising red-light-emitting phosphor.