Combustion synthesis of Eu3+-doped (La0.25Gd0.25Y0.25Lu0.25)2Zr2O7 phosphors with superior red-light emission and optical thermal stability through high-entropy engineering

The red-emitting phosphors with superior luminescence performance under the near-ultraviolet excitation play a crucial role in the field of solid-state lighting. Inspired by the idea of high-entropy engineering with multicomponent and microstructural complexities, a novel rare earth (La 0.25 Gd 0.25 Y 0.25 Lu 0.25 ) 2 Zr 2 O 7 : xEu 3+ (x = 1 −9 mol%) compound system was successfully designed and fabricated by solution combustion reaction, in which the Eu 3+ acted as the emission center and urea was used as fuel. The as-prepared high-entropy oxides (HEOs) possess single fluorite phase (space group Fm-3m) with homogeneous rare earth element distribution. Under the excitation with near-ultraviolet 393 nm, the HEO phosphor can generate the strong red-light emission at 613 nm, which corresponds to the 5 D 0 → 7 F 2 characteristic transition of Eu 3+ . The Eu 3+ doping concentration and molar ratio of urea to total metal ion are optimized to be x = 7 mol% and 5:1, respectively. The luminescence internal quantum yield (QY) reaches 37.5% and further increases to 44.0% via a subsequent thermal treatment at 1300 °C, which is dramatically higher than that of Eu 3+ -doped La 2 Zr 2 O 7 (QY = 8.9%), Gd 2 Zr 2 O 7 (QY = 7.7%) low-entropy composites and commercial Y 2 O 2 S:Eu 3+ phosphor. The optical thermal stability of rare earth HEO was also analyzed, indicating the high-entropy compound system with significant potential for the use of near-ultraviolet excited phosphor-converted light-emitting diodes.