Synthesis and optical properties of novel double perovskite Ca2MgTeO6:Dy3+,Na+ phosphors for white LEDs

Novel yellow-emitting phosphors of Dy3+-doped double perovskite Ca2MgTeO6 were synthesized by using a conventional high-temperature solid-state reaction. The phase purity, particle morphology, size distribution, elemental composition, luminescence properties, and luminescence decay curves of the resulting products were then analyzed in detail. The Ca2MgTeO6:Dy3+,Na+ phosphors show three emission peaks after near-ultraviolet excitation at 350 nm, which correspond to F-4(9/2) -> H-6(11/2), F-4(9/2) -> H-6(13/2), and F-4(9/2) -> H-6(13/2) transitions, respectively. Among them, the strongest peak is observed at 573 nm. The best doping content of Dy3+ in Ca2MgTeO6:xDy(3+),xNa(+) phosphors is x = 5 mol%. The calculated critical distance of energy transfer between Dy3+ ions is 1.6 nm. Luminescence quenching is confirmed to be due to dipole-dipole interactions among Dy3+ ions. The phosphors show excellent thermal stability with high activation energy (0.27 eV). The Commission Internationale de l'Eclairage (CIE) chromaticity coordinates of the Ca2MgTeO6Dy3+,Na+ phosphors are located in the yellow region. White light-emitting diodes (w-LEDs) were fabricated with a high color rendering index (R-a) of 88 and a good correlated color temperature (CCT) of 5440 K. All observed properties indicate that Ca2MgTeO6:Dy3+,Na+ phosphors have potential applications in display and photonic devices. (C) 2020 Published by Elsevier B.V. on behalf of Chinese Society of Rare Earths.