Preparation, crystal structure, and photoluminescence properties of high-brightness red-emitting Ca2LuNbO6:Eu3+ double-perovskite phosphors for high-CRI warm-white LEDs

Near-ultraviolet-excited efficient red phosphors are important for fabricating warm-white light-emitting diodes (LEDs) with high color rendering index. Herein, we demonstrated the preparation of novel highly efficient Eu3+ ions-activated Ca2LuNbO6 (CLN) double-perovskite phosphors. These phosphors were prepared by the high-temperature solid-state reaction method and they were characterized by powder X-ray diffraction, Rietveld refinement, excitation and emission spectra, decay lifetimes, internal quantum efficiency, and temperature-dependent emission spectra. The as-prepared phosphors can be efficiently excited by 396 nm near-ultraviolet light and generated bright red luminescence around 591, 616, 656 and 703 nm corresponding to the 5D0→7FJ (J = 1–4) transitions of Eu3+ ions. The optimal doping concentration of CLN:xEu3+ (x = 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8) phosphors was x = 0.4, and the optimal CLN:0.4Eu3+ sample exhibited high-color-purity (96.4%) red emission with internal quantum efficiency as great as 66%. The thermal-quenching resistance was evaluated by measuring their temperature-dependent emission intensities, while the emission intensity at 150 °C was about 65% of that at room temperature. Finally, a warm white LED lamp was made by using a 395 nm LED chip together with a phosphor blend of commercial blue phosphor BaMgAl10O17:Eu2+ and commercial green phosphor (Ba,Sr)2SiO4:Eu2+ and newly developed red phosphor CLN:0.4Eu3+, which gave bright high-quality white light with Commission Internationale de l’Eclairage (CIE) chromaticity coordinates of (0.3878, 0.3725), a correlated color temperature of 3769 K, and a color rendering index of 94 when the driven current was 20 mA. These investigation results clearly revealed the promising application potential of CLN:Eu3+ red phosphors in high-color-quality solid-state white lighting.