Synthesis of the phase pure Ba3Si6O12N2:Eu2+ green phosphor and its application in high color rendition white LEDs

Abstract

The promising green oxynitride phosphor, Ba₃Si₆O₁₂N₂:Eu²⁺, was synthesized at 1350 °C for 5 hours under a reducing N₂/H₂ (5%) atmosphere by using the solid-state reaction method. The phase purity was investigated by varying the nominal compositions, and the pure phase was achieved by carefully controlling the Si/Ba and O/Ba ratios. The phosphor displayed a broad excitation band spanning from the ultraviolet (UV) to the blue spectral region, and showed a single symmetrical emission band peaking at 525 nm with a full width at half maximum (FWHM) of ∼68 nm. The as-prepared green phosphor exhibited a small thermal quenching, which remained 90% of the initial emission intensity when measured at 200 °C. The internal and external quantum efficiencies measured under 450 nm excitation were 68 and 38%, respectively. Color temperature-tunable white LEDs with a high color rendering index of R_a = 88–94 were attained by combining the prepared green phosphor and a red phosphor Sr₂Si₅N₈:Eu²⁺ with a blue LED chip.