Host-Sensitized Luminescence Properties in CaNb₂O₆:Ln³⁺ (Ln³⁺ = Eu³⁺/Tb³⁺/Dy³⁺/Sm³⁺) Phosphors with Abundant Colors

Abstract

A series of Ln(3+) (Ln(3+) = Eu(3+)/Tb(3+)/Dy(3+)/Sm(3+)) ion doped CaNb2O6 (CNO) phosphors have been prepared via the conventional high-temperature solid-state reaction route. The X-ray diffraction (XRD) and structure refinement, diffuse reflection, photoluminescence (PL), and fluorescent decay curves were used to characterize the as-prepared samples. Under UV radiation, the CNO host present a broad emission band from about 355 to 605 nm centered around 460 nm originating from the NbO6 octahedral groups, which has spectral overlaps with the excitation of f-f transitions of Eu(3+)/Tb(3+)/Dy(3+)/Sm(3+) in CNO:Eu(3+)/Tb(3+)/Dy(3+)/Sm(3+) samples. They show both host emission and respective emission lines derived from the characteristic f-f transitions of activators, which present different emission colors owing to the energy transfer from the NbO6 group in the host to Eu(3+)/Tb(3+)/Dy(3+)/Sm(3+) with increasing activator concentrations. The decreases of decay lifetimes of host emissions in CNO:Eu(3+)/Tb(3+)/Dy(3+)/Sm(3+) demonstrate the energy transfer from the hosts to Eu(3+)/Tb(3+)/Dy(3+)/Sm(3+). The energy transfer mechanisms in CNO:Eu(3+)/Tb(3+)/Dy(3+) phosphors have been determined to be a resonant type via dipole-dipole mechanisms. For CNO:Sm(3+), the metal-metal charge transfer transition (MMCT) might contribute to the different variations of decay lifetimes and emission intensity from CNO:Eu(3+)/Tb(3+)/Dy(3+) samples. The best quantum efficiency is 71.2% for CNO:0.01/0.02Dy(3+). The PL properties of as-prepared materials indicate the promising application in UV-pumped white-emitting lighting diodes field.

Emerging cool white light emission from Dy3+ doped single phase alkaline earth niobate phosphors for indoor lighting applications

“…However, this approach encounters some serious issues such as the halo effect of blue/yellow color separation, color dependence on chromaticity, and poor color-rendering index (<65) due to the lack of green and red-emitting phosphor components at long wavelength regions, which limits the LED applications further. 8 On the other hand, UV/NUV LED coated with multi-color-emitting phosphors is an alternative approach to obtain white-light emission with an excellent color-rendering index (>90) as the luminous efficiency of NUV/UV chip pumped w-LEDs is higher than the blue chip. 9 However, UV/NUV excitable multiple color-emitting phosphors have some disadvantages such as low luminous efficiency due to blending together of blue, green and red-emitting phosphors and different degradation schedules of each phosphor.…”

Coordination polymer core/shell structures: Preparation and up/down-conversion luminescence

“…Among these characteristic emission spectrum peaks, the strongest one is centered at 612 nm ( 5 D 0 ? 7 F 2 ) and is ascribed to the typical electric-dipole transition, which is very sensitive in the host structure symmetry [40,41]. The transition observed at 593 nm ( 5 D 0 ?…”

Synthesis, characterization and properties of Dy3+-activated single host borosilicate phosphors

“…Therefore, many efforts have been made to develop the single-phased white emitting phosphors for w-LEDs [1][2][3]. At present, there are many hosts that can be activated by Dy 3+ ions, such as borates, phosphates, aluminates, silicates, etc [4][5][6][7]. Of all the hosts, borates due to their stable physical and chemical properties, excellent thermal stability and better absorption in UV region, therefore, it have attracted extensive attention.…”