The mechanism of luminance decrease in blue emitting BaMgAl10O,7:Eu2 phosphor after annealing has been studied. It was shown experimentally that annealing in air oxidizes BaMgAl10O17:Eu2 and substantially changes the Eu2 ion to an Eu3 ion. This is also deactivates the Eu2 luminescent center, thus decreasing Eu2 emission. Furthermore, the compound EuMgAl11O19, in which the valence of the Eu ion is trivalent, was detected in BaMgAl10O17:Eu2 annealed at temperatures higher than 800°C as a resulting product of oxidation. It was demonstrated that BaMgAl10O17:Eu2 was converted by oxidation into a mixture of the two compounds BaMgAl,0017 and EuMgAl11O19, and resulting in a further decrease in luminance. This suggests that obstructing the formation of Eu(III)MgAl11O19 during the annealing is essential for alleviating the decrease in luminance. Preparing BaMgAl,0O17:Eu2 having both superior crystallinity and completely stoichiometric composition has been found to be effective in alleviating the luminance decrease. InfroductionAn efficient blue phosphor BaMgAl10O17:Eu2 was developed at 1974, applied to tricolor fluorescent lamps (FL) as a blue component12 and has been widely used in the industry up to the present time.35 BaMgAl,0O17:Eu2 has also been a key phosphor of plasma display panel (PDP) in recent years for its high luminance efficiency under vacuum ultraviolet light exitation.79BaMgA119O17:Eu2 has conventionally been produced by ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.102.42.98 Downloaded on 2014-11-05 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.102.42.98 Downloaded on 2014-11-05 to IP

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The effects of firing temperature on the crystallinity and the luminescent properties of BaMgAl 10 O 17 :Eu 2ϩ phosphor have been investigated over the temperature range 1000-1800ЊC under preparative conditions which do not use any flux such as AlF 3 . The effects of particle shape and size of the ingredient Al 2 O 3 on the phosphor have also been studied under a preparative condition which has a firing temperature of 1700ЊC and does not use any flux. A single-phase BaMgAl 10 O 17 :Eu 2ϩ with sufficient luminescent properties can be obtained over a firing temperature range of 1600-1800ЊC through formation of the intermediate product BaAl 2 O 4 :Eu 2ϩ . Furthermore, the particle shape and size of the ingredient Al 2 O 3 determine the particle shape and size of BaMgAl 10 O 17 :Eu 2ϩ . Hightemperature firing in the absence of any flux has provided for the preparation of a single-phase BaMgAl 10 O 17 :Eu 2ϩ with various particle shapes, such as spherical or platelike, and particle sizes ranging from 2 to 18 m.

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