A single-crystalline defect-less phosphor is desired for efficient luminescence of the therein doped optical activators. In this paper, microsized MgAl2O4:Mn4+ single-crystal phosphors with bright red luminescence were grown in molten LiCl salt at 950 °C, for application in blue LED pumped white lighting. By comparing the phosphor formation from various Mg2+- and Al3+-bearing sources, both the template-formation and the dissolution-diffusion processes were evidenced to account for the formation of the microsized MgAl2O4:Mn4+ crystallites. Using nano γ-Al2O3 as the Al3+-bearing precursor, the uniform MgAl2O4:Mn4+ microcrystallites with a {111} planes-exposed tetragonal bipyramid morphology were obtained. The photoluminescence property was studied at various temperatures, and Mg ↔ Al anti-site disorder induced luminescence broadening was discussed. The Mn4+ 2Eg → 4A2g transition in MgAl2O4 shows a quite short luminescence wavelength peaking at 651 nm and ultrabroadband emission extending to 850 nm. The luminescence is relatively robust against thermal effect with relatively high thermal quenching temperature of 400 K and activation energy of 0.23 eV. Employing the red-emitting MgAl2O4:Mn4+ crystallites, blue LED pumped white lighting prototypes were fabricated which simulate the solar-like spectrum and show neutral to warm white.

Nowadays, the phosphor-converted white light-emitting diodes (LEDs) are pursuing better color rendering and lower correlated color temperature, by adding a red-emitting phosphor into the "blue LED + yellow-emitting garnet phosphor" system. Both Eu 2+ and Mn 4+ have been utilized as the blueto-red converting ions. Typically, the CaAlSiN 3 :Eu 2+ and (Ca, Sr) 2 Si 5 N 8 :Eu 2+ nitrides and the K 2 SiF 6 :Mn 4+ fluoride have been commercially employed in white LEDs for indoor lighting and wide-gamut displays. 1,2 The red phosphors activated by Mn 4+ show advantage over those activated by Eu 2+

The Mn 4+ -activated fluoride phosphor, typically K 2 SiF 6 :Mn 4+ , has become a renowned red-emitting phosphor for white light emitting diodes (LEDs) due to its sharp...

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