ABSTRACT
It was shown in previous chapters that the cathodoluminescent (CL) properties of phosphor powders have undergone optimization for more than 35 years because the transition probability of luminescence centers is governed by the short-range perfection around these luminescence centers. Small variations in CL properties result from oxygen contamination. Powdered mixtures charged in crucibles inevitably contain oxygen at 3
×
mole per mole a-ZnS powder. Because the blend mixture contains sulfur powder of more than 3
×
mole per mole a-ZnS powder, the oxygen is completely eliminated by heating the mixture using a heat program prior to crystallization of the phosphor particles. There is little room for further improvement in the CL properties of phosphor powders. The remaining problem concerns the screening of phosphor powders onto the CRT faceplate. Screenable phosphor powders are composed of polycrystalline particles 4 µm in size, rather than spherical [127-133] and microcrystalline particles. Spherical particles exhibit poor adhesion to the faceplate, and the particles easily move from the position on the substrate by moving water.
