Conventional Eu3+-activated phosphors often suffer from severe concentration quenching at high doping levels, significantly limiting their achievable brightness and efficiency. Furthermore, achieving both high color purity and strong emission intensity in the orange-red region remains challenging. In this context, we report the successful synthesis of Eu3+-activated Ba3Lu2B6O15 phosphors via a multistep solid-state reaction under ambient conditions, exhibiting intense reddish-orange emission. Upon near-ultraviolet excitation at 398 nm, the phosphors exhibited dominant emission at 593 nm with a long decay time (about 4.1 ms), attributed to the magnetic dipole-allowed 5D0 → 7F1 transition of Eu3+ ions occupying inversion-symmetric Lu3+ lattice sites. Remarkably, concentration quenching of Eu3+ luminescence in Ba3Lu2(1-x)Eu2xB6O15 was completely suppressed even at 70 mol % Eu3+ doping (x = 0.70), which can be understood from the unique one-dimensional chain-like architecture of the host lattice that restricts inter-Eu3+-ion energy migration to defect states. The as-synthesized Ba3Lu0.6Eu1.4B6O15 composition demonstrated an internal quantum efficiency of ∼53%, coupled with superior color purity (97.5%) as evidenced by CIE coordinates of (0.605, 0.387). Furthermore, the material displayed outstanding thermal stability, retaining ∼98% of its room-temperature emission intensity at 450 K. These combined attributes position Ba3Lu2B6O15:Eu3+ as a promising phosphor for next-generation warm-white LEDs.

The red-emitting Sr ₂ Si ₅ N ₈ :Eu ²⁺ phosphor with a superior quantum efficiency and suitable emission spectrum has been widely used as a promising down-conversion material in white light-emitting diodes. However, its thermal degradation under high temperature handicaps its large scale application, and therefore must be reduced. Here, we proposed to increase the thermal stability of Sr ₂ Si ₅ N ₈ :Eu ²⁺ by coating a nanometer-order Al ₂ O ₃ film on each phosphor particle using an atomic layer deposition approach in a fluidized bed reactor. The deposited Al ₂ O ₃ layer was quite uniform and conformal when using O ₃ as the oxidizer, and its thickness could be controlled by the dosage type, deposition temperature and cycle numbers, which largely affects the photoluminescence properties and thermal degradation of the title phosphor. Thermal gravimetric analysis results showed that the oxidation temperature of the coated phosphor increased from 700 to 850 °C, suggesting that the coating layer has the function of anti-oxidation. Meanwhile, the coated phosphor particle surface became hydrophobic. Consequently, the thermal degradation of phosphor powders in air at 200 °C was greatly reduced and the stability of the fabricated LEDs with coated powders was also improved. Prospectively, the proposed approach provides a new strategy to improve the thermal stability of other phosphors.

The β-sialon:Eu²⁺ phosphor has superior luminescent properties as an excellent green down-conversion material for white light-emitting diodes. To take advantage of its high chromaticity and apply it to field emission displays (FEDs), the drawback of its electron insulation that impedes the electron transmission when excited by e-beam needs to be solved. In this work, a facile method was adopted to coat conductive In₂O₃ on the surface of β-sialon:Eu²⁺ phosphor, and the influence of In₂O₃ coating on the cathodoluminescent properties was investigated. The results show that the In₂O₃ coating contributes to charge elimination and significantly improves the cathodoluminescence (CL) of β-sialon:Eu²⁺. Under 19 kV/1.0 nA e-beam excitation, the In₂O₃ coated sample shows CL intensity about four times higher than that of the uncoated β-sialon:Eu²⁺. Moreover, no luminescence saturation occurs in coated β-sialon:Eu²⁺, indicating that the In₂O₃-coated β-sialon:Eu²⁺ would be a promising green emissive material for full-color FEDs.

To modify the luminescence properties of Ce³⁺-doped Y₃Al₅O₁₂ (YAG) phosphors, they have been coated with a carbon layer by chemical vapor deposition and subsequently heat-treated at high temperature under N₂ atmosphere. Luminescence of the carbon coated YAG:Ce³⁺ phosphors has been investigated as a function of heat-treatment at 1500 and 1650 °C. The 540 nm emission intensity of C@YAG:Ce³⁺ is the highest when heated at 1650 °C, while a blue emission at 400-420 nm is observed when heated at 1500 °C but not at 1650 °C. It is verified by X-ray diffraction (XRD) that the intriguing luminescence changes are induced by the formation of new phases in C@YAG:Ce³⁺-1500 °C, which disappear in C@YAG:Ce³⁺-1650 °C. In order to understand the mechanisms responsible for the enhancement of YAG:Ce³⁺ emission and the presence of the blue emission observed for C@YAG:Ce³⁺ -1500 °C, the samples have been investigated by a combination of several electron microscopy techniques, such as HRTEM, SEM-CL, and SEM-EDS. This local and cross-sectional analysis clearly reveals a gradual transformation of phase and morphology in heated C@YAG:Ce³⁺ phosphors, which is related to a reaction between C and YAG:Ce³⁺ in N₂ atmosphere. Through reaction between the carbon layer and YAG host materials, the emission colour of the phosphors can be modified from yellow, white, and then back to yellow under UV excitation as a function of heat-treatment in N₂ atmosphere.

Synthesizing pure phase Ba₃Si₆O₉N₄ by the conventional solid-state reaction method is challenging because of easily formed secondary phase Ba₃Si₆O₁₂N₂ showing similar crystal structure. In this work, an alternative low temperature synthesis method is presented, and a series of green to blue emitting (Ba, Sr)₃Si₆O₉N₄: Eu²⁺ phosphors were prepared by a mechanochemical activation route. Variations in photoluminescence properties and crystal structure, as induced by the change in phosphor composition, were investigated. Under ultraviolet-light excitation, Ba₃Si₆O₉N₄: Eu²⁺ phosphor exhibited a strong narrow green emission at 518 nm and simultaneously a weak emission at 405 nm, which are ascribed to different Eu/Ba sites in Ba₃Si₆O₉N₄ lattice proved by Density Functional Theory (DFT) calculations. A continuous green to blue emission in (Ba, Sr)₃Si₆O₉N₄: Eu²⁺ phosphors could be achieved by tuning the crystal structure and local coordination environment acting on Eu²⁺ with Sr/Ba substitution. More Sr/Ba substitution improved thermal quenching and resulted in a different characteristic of emission peak shift upon increasing the temperature.