Terbium-activated lanthanum oxybromide phosphor is a highly efficient X-ray luminescent material

but its chemical property is very unstable

particularly in a moisture containing atmosphere.In this paper

a new method of preparing moisture-resistant terdium-activated lanthanum oxybromide Phosphor and X-ray intensifying screen is provided:Firstly

a small quantity of water-unsolvable substance

such as aluminium Phosphate

aluminium sili-cate

aluminium hydroxide

zinc Phosphate or zinc silicate etc

is deposited on the surface of phosphor particles.Secondly

the Phosphor particles with appropriate quantity of anhydrous magnesium sulfate are mixed by ball mill

so that the Phosphor particles surrounded by anhydrous magnesium sulfate powder. The method of Xrray intensifying screen is the same as that of calcium tungstate screen.The Phorsphor

after immersion in water at 75℃ for 105 hours

showed no decrease in the emission in tensity

whereas the Phosphor started to hydrolyze after 20 minutes.The phosphor and the X-ray intensifying screen after storage at 45℃ and 100% hymi-dity for 260 days

also showed no decrease in the emission intentity

but the untreated phosphor and screen started to show a marked decreese in the emission intensity after about 10 days.