| abstract |
The present invention is to provide a phosphor of minimum particle size having an excellent crystallinity and a high brightness higher than conventional crude particles, which is usable for a highly precise display, a highly bright illuminating element or illuminating apparatus, a high speed immunoassay system or the like, i.e. a phosphor having a substantially spherical outer shape, which comprises primary particles having a median diameter D 50 in a range of from 0.05 μm to 1 μm and secondary particles having a median diameter D 50 in a range of from 0.1 μm to 2 μm, wherein at least 50 vol % of the total secondary particles has an aspect ratio of at least 0.8 and an internal quantum efficiency is in a range of from 0.8 to 1. |