Orange‐Red‐emitting Ca₉Gd(PO₄)₇:Eu³⁺ Phosphors: Judd‐Ofelt Analysis and Investigation on the Thermal Stability, Quantum Efficiency for WLED

Abstract

Orange‐red‐emitting Eu3+‐doped Ca9Gd(PO4)7 phosphors have been obtained by a sol‐gel technique. These phosphors, excited by UV (270 nm) and near UV light (394 nm), emit orange‐red light in the range of 580–710 nm. The Ca9Gd(PO4)7:7 mol% Eu3+ phosphor annealed at 1100 °C shows the highest PL intensity. Judd‐Ofelt analysis reveals that the neighbor surroundings of Eu3+ ions are asymmetric, and the lowest asymmetry value is found at the dopant ratio of 7 mol%. The optimal phosphor excited by the wavelength of 394 nm displays an excellent thermal stability (∼76.4 % at 160 °C) with an activation energy of 0.163 eV. The corresponding CIE chromaticity coordinates (x; y) and color purity are calculated to be (0.5849; 0.3635) and 84.6 %, respectively. The quantum efficiency values of the Ca9Gd(PO4)7:Eu3+ phosphors coated on UV and near‐UV chips are 87.4 % and 5.1 %, respectively. It is the first time that the QE values of Ca9Gd(PO4)7:Eu3+‐based red and blue‐emitting LEDs are reported.

High quantum efficiency and excellent color purity of red-emitting Eu3+-heavily doped Gd(BO2)3-Y3BO6-GdBO3 phosphors for NUV-pumped WLED applications

“…48 The most intense PL intensity is obtained at 20 mol%, indicating that the distance between neighbor Eu 3+ ions reached its critical distance threshold, R c . 8,11,48 In this case, the R c value of 7.02 Å can be determined using the Blasse equation, which is higher than the critical value of 5 Å for exchanging energy by interaction, implying the governance of the multipolar interaction for the quenching mechanism. 8,16 It is well known that multipolar interaction oen contains three types that correspond to the value of the characteristic function for multipolar interaction types: dipole-dipole, dipole-quadrupole, and quadrupolequadrupole interactions.…”

“…4b reveals a uctuation of peak position at the dopant level of 1-23 mol% and a shi towards a larger 2q angle with a further increase in Eu 3+ ion concentration. Although Eu 3+ ions could replace Y 3+ or/and Gd 3+ ions in the host lattice, 3,6,11 they are preferentially substituted by Y 3+ ions owing to a slight difference in radius between Eu 3+ and Y 3+ ions. 29,30 Hence, the negligible variation in the (−211) peak at Eu 3+ doping concentrations of 1-23 mol% could be explained well by substituting Eu 3+ with Y 3+ ions.…”

“…In contrast, the right shift at the higher Eu 3+ doping content (>23 mol%) implies the dominance of the substitution of Eu 3+ ions for Gd 3+ ions when the saturated replacement of Eu 3+ for Y 3+ ions is reached in the host lattice. 11,31…”

“… 10 In addition, the use of blue excitation causes significant reabsorption and reduces the quality of output light. 11 Eu 3+ -doped phosphors could solve this issue because of the featured excitation in the NUV region (360–420 nm). 5 Owing to the characteristic 5 D 0 → 7 F J ( J = 1, 2, 3, and 4) transitions, Eu 3+ -doped phosphors could produce narrow-band orange-red/red emissions, in which the orange-red (610–630 nm) emission, corresponding to the 5 D 0 → 7 F 2 transition, is appropriate for indoor or full-color display applications with high color purity.…”

Novel Red‐Emitting Gd3BW1‐xMoxO9 : Eu3+ Phosphor with High Thermal Stability for Application in UV‐Excited WLEDs and Rapid Visualization of Latent Fingerprints

“…Nowadays, as global electricity consumption continues to increase in artificial lighting field along with alarming concerns over energy crisis and environmental change place a great application value on the development of new high efficiency lighting sources to reduce the world's power consumption. [1][2] Compared to traditional incandescent and fluorescent lamps, solid-state white light-emitting diodes (WLEDs) are expected to be the most promising illumination sources due to their attractive merits of lower energy consumption, longer working life time (> 100000 h), faster response time, higher brightness and environmental friendliness characteristics. [3][4][5][6][7][8][9][10] Currently, there are mainly two widely used techniques to realize WLEDs.…”