The study of phosphate-based phosphor powders coated by atomic layer deposition of Al₂O₃

Phosphate-based phosphors have great potential in the application of white light conversion light emitting diodes (LEDs), but the highly hydrolysable speciality restricts its applications. In this work, an atomic layer deposition (ALD) vibrating fluidized bed is used to deposit alumina as a barrier layer of the phosphate-based phosphor powders. The surface morphology and conformality of coatings are characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. The barrier property is examined by pH measurement after immersing the sample into the deionized water. The influence of coating on luminescent properties is studied by the steady state/transient fluorescence spectrometer. It was observed that ALD Al 2 O 3 can efficiently block the humid permeation and prevent the powders from the hydrolysis. Interestingly, the luminous properties are slightly improved after the powders are coated by Al 2 O 3 , i.e. a slight increase of PL intensity, a red-shift of the emission peak, except the fluorescence lifetime, which is slightly shortened.