Luminescence properties of Ca2GdNbO6: Sm3+, Eu3+ red phosphors with high quantum yield and excellent thermal stability for WLEDs

Abstract

A series of Ca2GdNbO6: xSm3+ (0.01 ≤ x ≤ 0.15) and Ca2GdNbO6: 0.03Sm3+, yEu3+ (0.05 ≤ y ≤ 0.3) phosphors were synthesized by the traditional solid-state sintering process. XRD and the corresponding refinement results indicate that both Sm3+ and Eu3+ ions are doped successfully into the lattice of Ca2GdNbO6. The micro-morphology shows that the elements of Ca2GdNbO6: 0.03Sm3+, 0.2Eu3+ phosphor are evenly distributed in the sample, and the particle size is about 2 μm. The optical properties and fluorescence lifetime of Ca2GdNbO6: 0.03Sm3+, Eu3+ phosphors were detailedly studied. The emission peak at 5D0→7F2 (614 nm) is the strongest and emits red light under 406 nm excitation. The increase of Eu3+ concentration causes the energy transfers from Sm3+ to Eu3+ ions, and the transfer efficiency reaches 28.6%. Ca2GdNbO6: 0.03Sm3+, 0.2Eu3+ phosphor has a quantum yield of about 82.7%, and thermal quenching activation energy is of 0.312 eV. The color coordinate (0.646, 0.352) of Ca2GdNbO6: 0.03Sm3+, 0.2Eu3+ phosphors is located in the red area. The LED device fabricated based on the above phosphor emit bright white light, and CCT = 5400 K, Ra = 92.8. The results present that Ca2GdNbO6: 0.03Sm3+, Eu3+ phosphors potentially find use in the future.