Rolex Sa

Hans U Güdel

Detlef Berner

Romain Girod

Isabelle Rigot

Christoph Kenzelmann

The present invention relates to long decay phosphors comprising rare earth activated strontium aluminates and methods for producing them. The phosphors comprise a matrix of the formula SrAlOcomprising europium as an activator and a further rare earth element as a co-activator, wherein the molar ratio of Al/Sr in the starting materials is in the range of 3.1 to less than 3.5 and the ratio of Eu/Sr is in the range of 0.0015 to 0.01. The process for the preparation of a phosphor comprises the steps of milling the starting materials for the synthesis of the phosphor, the starting materials comprising a boron compound selected from boric acid, boric oxide or a borate salt in an amount such that the B/Sr molar ratio is between 0.1 and to 0.3, treating the milled composition with heat, grinding the block material which is obtained through the heat treatment, ball-milling the crushed material, sieving the material, and washing the material with an aqueous solution.

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Thörishaus, Switzerland

Hans U Güdel