Highly Efficient and Thermally Stable Blue-Green (Ba₀.₈Eu₀.₂O)(Al₂O₃)₄.₅₇₅×₍₁₊ₓ₎ Phosphor through Structural Modification

Exploring phosphors with high quantum efficiency (QE) and thermal stability is an important issue for their application in white light-emitting diodes (LEDs). In this work, the crystal structure and luminescent properties of Eu²⁺-activated aluminate phosphors with a normal composition (Ba₀.₈Eu₀.₂O)(Al₂O₃)₄.₅₇₅×₍₁₊ₓ₎ (short for BA₁₊ₓO:0.2Eu²⁺) were studied. Although the crystal structures of BA₁₊ₓO:0.2Eu²⁺ have a same space group, the increase of the Al content will lead to the decrease of cell volume, occupancy of Ba and O6 that is at around Ba1 site, and the increase of the average distance between Eu²⁺ ions, which are responsible for the modification of luminescent properties. BA₁₊ₓO:0.2Eu²⁺ exhibits a blue-green emission with an emission peak at around 450 nm and a shoulder at around 490 nm. The increase of Al/(BaEu) ratio results in the increase of both absolute QE and thermal stability. The absolute QE of BA₁.₅O:0.2Eu²⁺ is 99.4%, and the emission intensity at 150 °C remains more than 90% of that at room temperature, showing the best performance. Furthermore, all of the external QE values of BA₁₊ₓO:0.2Eu²⁺ (x = 0.2–0.5) are higher than 70%. The properties of the LEDs based on the as-prepared phosphor suggest its potential as a candidate for UV LED pumped phosphor-converted white LEDs.