Luminescence Properties of Spinels Doped with Manganese Ions

Abstract

A method to synthesize spinel (MgAl2O4)–based compounds doped with magnesium ions was developed, which makes it possible to create red-emitting phosphors (band peak at 651 nm) or green-emitting phosphors (band peak at 525 nm) due to the luminescence of Mn4+ or Mn2+, respectively, and also phosphors that have both (red and green) emission bands. Both types of luminescence exhibit quite high thermal stability; particularly, the green luminescence does. Namely, the temperature at which the luminescence intensity halves in comparison with the maximum intensity is T0.5 = 448 and 737 K for the red (Mn4+) and green (Mn2+) luminescence, respectively. On the other hand, for the phosphors that have both emission bands, the temperature dependences of the intensities of the red and green luminescence more closely resemble each other because of the energy transfer from Mn4+ ions to Mn2+ ions. Both emission bands are efficiently excited in the blue spectral region, which enables the use of the conventional three-color RGB (red–green–blue) method to create LED white-light sources based on a combination of a blue light-emitting diode and a phosphor containing manganese ions with an optimally chosen ratio between the intensities of the green and red emission bands.