摘要 |
A particulate luminescent composition is disclosed that, when excited by electromagnetic radiation at a first frequency, emits electromagnetic radiation at a second frequency equal to or within 1500 cm<SUP>-1 </SUP>of the first frequency. The luminescent composition comprises substantially spherical particles having a weight average particle size of less than about 10 mum and a particle size distribution such that at least about 90 weight percent of the particles are not larger than twice the average particle size.
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