Synthesis and luminescent properties of Eu²⁺ doped nitrogen-rich Ca-α-SiAlON phosphor for white light-emitting diodes

Yellow/orange-emitting nitrogen-rich Ca_0.9Si₉Al ₃(O,N)₁₆: Eu²⁺ phosphors were successfully prepared by solid-state reaction synthesis. The fluorescence excitation spectra of all of the nitrogen-rich Ca_0.9Si₉Al₃(O,N) ₁₆: Eu²⁺ phosphor powders displayed two broad bands centered at about 300 nm and 400-475 nm. The first peak was assigned to the absorption of the host lattice and the second to the 4f⁷ → 4f⁶5d¹ absorption of the Eu²⁺ ions, its means enhanced 4f⁷ → 4f⁶5d excitation of Eu²⁺ ion. The absorption peak intensity increased upon increasing the Eu²⁺ doping amount, but only up to a Eu²⁺ concentration ratio of 0.15. The emission spectra of the prepared Ca_0.9Si₉Al ₃(O,N)₁₆: Eu²⁺ phosphors all exhibited a single broad band in the 500-700 nm region, maximum emission peak observed at 591 nm. The room temperature decay times were observed τ₁ = 1.27 μs and τ₂ = 9.90 μs.