Double Surface Coating to Improve the Photoluminescence Performance of BaMgAl10O17 : Eu2+ Phosphors

Abstract

Europium-doped barium magnesium aluminate was double-coated with silicon dioxide and alumina by a sol-gel method. X-ray diffraction patterns show no phase change for coated phosphors. The scanning electron microscope and energy dispersive X-ray spectrophotometer result that the single coated material was uniform silicon dioxide thin film and the double coated surface was consisted of silicon dioxide and alumina hybrid films. The transmission electron microscope images revealed that the thickness of the first layer and the second layer was 60 and 15 nm, respectively. The results of thermal stability test indicated that relative-brightness loss of uncoated, single coated and double coated phosphors was 18.29, 6.83 and 2.76 %, respectively. Colour coordinate shift (Dx, Dy) of these samples was (0.0003, 0.0082), (0.0001, 0.0042) and (0.0001, 0.0028), respectively. Barium magnesium aluminate phosphor's colour coordinate shift was reduced while thermal stability was improved by double coating, which was better than that of single coated sample, because the double coating method overcame the problem of luminescence intensity decline in the process of thickening the single coated layer.