A novel red phosphor Ba₃La₂W₂O₁₂:Eu³⁺ with intense ⁵D₀-⁷F₄ transition and excellent thermal stability for white LEDs

Red-emitting phosphors with high thermal stability are of great significance for improving the performance of phosphor-converted white light-emitting diodes (pc-WLEDs). A series of Ba₃La₂W₂O₁₂:xEu³⁺ (BLWO:xEu³⁺, 0 ≤ x ≤ 0.12, Δx = 0.02) red phosphors excitable by UV-near UV and blue light were successfully synthesized via high-temperature solid-state reaction. The crystal structure, micromorphology, and optical properties of the BLWO:Eu³⁺ phosphor were systematically investigated. The emission spectrum of the BLWO:Eu³⁺ phosphor is dominated by the red emission at 616 nm originating from the electric dipole ⁵D₀ → ⁷F₂ transition of Eu³⁺. Notably, the ⁵D₀ → ⁷F₄ emission at 702 nm exhibits remarkable intensity, reaching approximately 70% of the strongest ⁵D₀ → ⁷F₂ emission (616 nm). The optimal Eu³⁺ doping concentration in the BLWO:Eu³⁺ phosphor was determined to be 0.06, with the concentration quenching mechanism governed by electric quadrupole-quadrupole (q-q) interactions. The BLWO:0.06Eu³⁺ phosphor demonstrates excellent quantum efficiencies with an internal quantum efficiency (IQE) of 62.91% and an external quantum efficiency (EQE) of 35.23%, along with outstanding thermal stability. Benefiting from these superior properties, the phosphor was successfully employed in WLED fabrication. The resulting device exhibits warm white light with CIE 1931 chromaticity coordinates of (0.3453, 0.3518) and a high color rendering index (R_a) of 80.3.