Enhancement of the photoluminescence properties of Ba_1.98SiO_4−δN_2/3δ: Eu_0.02 phosphors and their application to green LEDs

A green emitting Ba_1.98SiO_4−δN_2/3δ:Eu_0.02 phosphor with an appreciable intensity was synthesized using the gas-reduction–nitridation (GRN) method. SEM revealed agglomerated Ba_1.98SiO_4−δN_2/3δ:Eu_0.02 particles with irregular morphologies and a primary particle size of 1–2.5 μm. The phosphor showed emission lines of Eu²⁺ corresponding to the 4f⁶5d¹ → 4f⁷ transition under 370 nm excitation. As the GRN process was conducted to incorporate N³⁻ into the lattice, both the excitation and emission intensity of Ba_1.98SiO_4−δN_2/3δ:Eu_0.02 were enhanced greatly compared to Ba_1.98SiO₄:Eu_0.02. The decay time of Ba_1.98SiO_4−δN_2/3δ:Eu_0.02 showed that N entered the Ba_1.98SiO₄:Eu_0.02 lattices to replace O to form a N_O point defect. The electroluminescence intensity of Ba_1.98SiO_4−δN_2/3δ:Eu_0.02 at 503 nm increased with increasing forward bias current. Intense green LEDs were fabricated by coating the synthesized phosphors on the cap of the near-ultraviolet InGaN LEDs (λ_em = 375 nm). Overall, this phosphor appears to be a promising candidate for solid-state lighting applications.