Mn, Cr-co-doped MgAl2O4 phosphors for white LEDs

The Mn-, Cr-doped and Mn, Cr-co-doped MgAl₂O₄ powders have been synthesized via a gel-solid reaction method. Energy transfer from Mn²⁺ to Cr³⁺ has been observed for the first time in the co-doped MgAl₂O₄ phosphors. When excited with blue light with a wavelength of 450 nm at room temperature, both green emission from Mn²⁺ around 520 nm and red emission from Cr³⁺ around 675and 693 nm were generated. Moreover, the color of the emission can be modified by controlling the doping concentrations of Mn²⁺ and Cr³⁺. Therefore, MgAl₂O₄: Mn²⁺, Cr³⁺ could be used as a single-phased phosphor for white LED with a blue LED chip. The energy transfer in terms of Mn²⁺ to Cr³⁺ is determined by means of radiation and reabsorption.