The Luminescence of Self-Coactivated ZnS:Cu

Phosphors prepared by firing ZnS with Cu in purif ied H~S show a simple orange emission band, with no other bands in evidence even at 90 ~ Excita-tion by ultraviolet, cathode rays, and electric field gives identical emission spectra. The emission band peaks at the same wave length for samples with either hexagonal or cubic crystal structure, but is shifted to longer wave lengths by addit ion of CdS. The orange luminescence is strongly decreased by traces of H~O in the H~S firing atmosphere, but quite stable to firing in oxidiz-ing or reducing atmospheres. Addit ion of A1 to ZnS:Cu gives a series of phosphors showing various proportions of orange, blue, and green emission. F i r ing ZnS with Ag in pure H~S gives a new yel low-emitt ing phosphor with propert ies very similar to the orange Cu-activated phosphor. Possible models for the orange center are discussed. A few years ago, Froe l ich (1) descr ibed a ne