For solving the problem on the degradation of light efficient of BAM phosphor

BAM phosphor was coated with alumina sol(the diameter of the particle is about 10nm) making an alumina protective film around the individual powder particle of BAM.The surface state and surface component of the coated powder were investigated with SEM and Xps.The alumina film coating rate on the power surface reached to be about 90% and the film layer was found quite stable as it could stand various processes

e.g.

washing with water

coating in lamp tube and baking at high temperature. The BAM phosphor’s luminescence performance was tested and compared to uncoated phosphor. An evident improvement has been found in the thermal stability. The thermal deterioration of the phosphor was alleviated obviously after annealing at 500

550

600 and 650℃ for 30min. By the way

the fluorescent lamps of single colour were prepared using the coated phosphor for the time lighting test. The degradation of light efficient was less than uncoated one evidently. For example

the degradation of the lamps after lighting for 1 000h

for the coated BAM phosphor was 6.1%

but 18.5% for uncoated one. The mercury amount adsorbed on the phosphor was determined by cold vapour atomic absorption spectrometry(CVAAS)

and the result proved that the adsorbed amount on coated BAM phosphor was evidently less than that for uncoated one. Based on a series of results in the test

it was proved that the coating treatment of BAM phosphor can protect the phosphor powder and can improve the thermal stability and alleviate the decrease in luminance of the BAM phosphor. Therefore

the study by coating treatment for BAM phosphor with alumina sol is of significance in practice.