U.S. Philips Corporation

Marinus G Tak

Robert C Peters

Gerardus P Hoeks

Cornelis Wilhelmus Schetters

Abraham Sonneveld

A luminescent screen provided with a luminescent layer (4) disposed on a support (1) and containing an alkaline earth metal aluminate activated by bivalent europium. The alkaline earth metal is barium which may be replaced up to 25 mol. % by strontium. The aluminate has a crystal structure, the X-ray powder diagram of which corresponds or substantially corresponds to the diagram given in Table I of the description, while the ratio of alkaline earth metal to aluminium in the aluminate has a value of 1:5 to 1:10. An advantageous use of such a luminescent screen is found in low-pressure mercury vapor discharge lamps.

Bivalent europium-activated barium aluminate phosphor and low mercury

A low-pressure mercury vapor discharge lamp provided with a luminescent Eu-activated rare earth oxide, a luminescent aluminate with hexagonal crystal structure activated by Ce or by Ce and Tb, or a luminescent aluminate with hexagonal crystal structure activated by Eu or by Eu and Mn. Not more than 5% by weight of the luminescent material has a grain size smaller than 1 .mu.m and the maximum of the grain size distribution curve is located in the range from 2 to 8 .mu.m.

Fluorescent discharge lamp having luminescent material of a specified

Luminescent aluminate with magnetoplumbite crystal structure, activated by cerium, by cerium and terbium or by cerium and manganese. The aluminate comprises at least one of the elements B, Si and P in a quantity of 0.001 to 0.20 mole per mole of aluminate which results in improved properties of luminescence. These aluminates are preferably used in low-pressure mercury vapor discharge lamps.

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Eindhoven, Netherlands

Marinus G Tak