Alkaline earth haloapatite phosphors - thermally refined by a continuous process

The phosphor precursor material is formed in friable, coherent, uniform size briquettes and fed continuously into a furnace at >800 degrees C. The rate of passage is such as to allow the material to be heated to incandenscence, after which the briquettes are crushed to yield phosphor powder of uniform particle size. Spec. the phosphor is a Sb-activated alkaline earth haloapatitie which is treated in the furnace at 1050-1200 degrees C and rapidly cooled before crushing. The furnace used is either a horizontal tunnel type with the briquettes transported through, or a slightly inclined rotary furnace into which the material is fed at the higher end. Material of uniform particle size and improved homogeneity and crystallinity is produced. The use of special crucibles requiring careful thermal treatment over long periods is eliminated, the furnace residence time being ca. 40 mins.