The cyan-emitting BaSi2O2N2:Eu2+ phosphor is a promising narrow-band and high-efficiency luminescent material used in wide-color-gamut white light-emitting diodes (wLEDs). However, its serious degradation under thermal attacks hinders its practical applications and needs to be improved. Herein, we proposed to deposit a nano-sized Al2O3 film around each BaSi2O2N2:Eu2+ particle through atomic layer deposition (ALD) in a fluidized bed reactor to improve its thermal stability. Thermal gravimetric analysis results showed that the Al2O3 layer with a thickness of only 11 nm had an obvious anti-oxidization effect, by which the oxidation temperature in air of the Al2O3 coated phosphor was largely increased from ∼550 to ∼750 °C. Moreover, the Al2O3 coated phosphor remained 93% of its luminescence intensity in comparison to 73% of the uncoated one when degraded under water-steam at 200 °C for 24 h. The oxidization of both the BaSi2O2N2 host matrix and the doped Eu2+ ions was reduced by the Al2O3 layer. Meanwhile, the wLEDs fabricated with the Al2O3 coated phosphor showed a luminous flux of 3 times higher than that of the uncoated one when aged under 100 mA for 300 h. The greatly improved thermal degradation property of BaSi2O2N2:Eu2+ phosphor and the reliability of the wLEDs indicate that the ALD approach could be a feasible route to produce uniform and nano layers on phosphors and enhance their stability.@en

The feasibility of coating K2SiF6:Mn4+ phosphor particles with an Al2O3 layer, in order to enhance the optical properties and improve the chemical and thermal stability, has been studied. Two types of K2SiF6:Mn4+ phosphor particles have been coated with a thin (3-25 nm) Al2O3 layer using atomic layer deposition in a fluidized bed reactor. The Al2O3 coating layer does not have any significant effect on the spectral excitation and emission features, but the emission intensity of conventional K2SiF6:Mn4+ (KSF-1) decreases, which is ascribed to the formation of undesirable MnO2. The thermal quenching of the KSF-1 phosphor in an inert atmosphere is reduced by the Al2O3 coating layer. Degradation during the deposition of Al2O3 is prevented by using K2SiF6:Mn4+ particles with an undoped K2SiF6 shell (KSF-2). The Al2O3 coating layer has a positive effect on the stability of both the KSF-1 and KSF-2 phosphors in a water environment, as the Al2O3 layer acts as a barrier against the hydrolysis of K2SiF6. In air, however, water present in the Al2O3 coating layer enhances the degradation of the phosphor at elevated temperatures.@en

The feasibility of coating K2SiF6:Mn4+ phosphor particles with an Al2O3 layer, in order to enhance the optical properties and improve the chemical and thermal stability, has been studied. Two types of K2SiF6:Mn4+ phosphor particles have been coated with a thin (3-25 nm) Al2O3 layer using atomic layer deposition in a fluidized bed reactor. The Al2O3 coating layer does not have any significant effect on the spectral excitation and emission features, but the emission intensity of conventional K2SiF6:Mn4+ (KSF-1) decreases, which is ascribed to the formation of undesirable MnO2. The thermal quenching of the KSF-1 phosphor in an inert atmosphere is reduced by the Al2O3 coating layer. Degradation during the deposition of Al2O3 is prevented by using K2SiF6:Mn4+ particles with an undoped K2SiF6 shell (KSF-2). The Al2O3 coating layer has a positive effect on the stability of both the KSF-1 and KSF-2 phosphors in a water environment, as the Al2O3 layer acts as a barrier against the hydrolysis of K2SiF6. In air, however, water present in the Al2O3 coating layer enhances the degradation of the phosphor at elevated temperatures.@en

The feasibility of coating K2SiF6:Mn4+ phosphor particles with an Al2O3 layer, in order to enhance the optical properties and improve the chemical and thermal stability, has been studied. Two types of K2SiF6:Mn4+ phosphor particles have been coated with a thin (3-25 nm) Al2O3 layer using atomic layer deposition in a fluidized bed reactor. The Al2O3 coating layer does not have any significant effect on the spectral excitation and emission features, but the emission intensity of conventional K2SiF6:Mn4+ (KSF-1) decreases, which is ascribed to the formation of undesirable MnO2. The thermal quenching of the KSF-1 phosphor in an inert atmosphere is reduced by the Al2O3 coating layer. Degradation during the deposition of Al2O3 is prevented by using K2SiF6:Mn4+ particles with an undoped K2SiF6 shell (KSF-2). The Al2O3 coating layer has a positive effect on the stability of both the KSF-1 and KSF-2 phosphors in a water environment, as the Al2O3 layer acts as a barrier against the hydrolysis of K2SiF6. In air, however, water present in the Al2O3 coating layer enhances the degradation of the phosphor at elevated temperatures.@en

The feasibility of coating K2SiF6:Mn4+ phosphor particles with an Al2O3 layer, in order to enhance the optical properties and improve the chemical and thermal stability, has been studied. Two types of K2SiF6:Mn4+ phosphor particles have been coated with a thin (3-25 nm) Al2O3 layer using atomic layer deposition in a fluidized bed reactor. The Al2O3 coating layer does not have any significant effect on the spectral excitation and emission features, but the emission intensity of conventional K2SiF6:Mn4+ (KSF-1) decreases, which is ascribed to the formation of undesirable MnO2. The thermal quenching of the KSF-1 phosphor in an inert atmosphere is reduced by the Al2O3 coating layer. Degradation during the deposition of Al2O3 is prevented by using K2SiF6:Mn4+ particles with an undoped K2SiF6 shell (KSF-2). The Al2O3 coating layer has a positive effect on the stability of both the KSF-1 and KSF-2 phosphors in a water environment, as the Al2O3 layer acts as a barrier against the hydrolysis of K2SiF6. In air, however, water present in the Al2O3 coating layer enhances the degradation of the phosphor at elevated temperatures.@en

The feasibility of coating K2SiF6:Mn4+ phosphor particles with an Al2O3 layer, in order to enhance the optical properties and improve the chemical and thermal stability, has been studied. Two types of K2SiF6:Mn4+ phosphor particles have been coated with a thin (3-25 nm) Al2O3 layer using atomic layer deposition in a fluidized bed reactor. The Al2O3 coating layer does not have any significant effect on the spectral excitation and emission features, but the emission intensity of conventional K2SiF6:Mn4+ (KSF-1) decreases, which is ascribed to the formation of undesirable MnO2. The thermal quenching of the KSF-1 phosphor in an inert atmosphere is reduced by the Al2O3 coating layer. Degradation during the deposition of Al2O3 is prevented by using K2SiF6:Mn4+ particles with an undoped K2SiF6 shell (KSF-2). The Al2O3 coating layer has a positive effect on the stability of both the KSF-1 and KSF-2 phosphors in a water environment, as the Al2O3 layer acts as a barrier against the hydrolysis of K2SiF6. In air, however, water present in the Al2O3 coating layer enhances the degradation of the phosphor at elevated temperatures.@en

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. @en