Luminescence and Trapping in Zinc Sulfide Phosphors with and without Copper Activator

Abstract

A comprehensive study of ZnS:[Zn] and ZnS:[Zn]: Cu phosphors has been carried out with the use of glow curves, phosphorescence emission decay curves, and spectral distribution curves of emission during excitation by 3650A ultraviolet. The principal contributions of the study are (1) glow curves and spectral emission curves for nine samples each of cubic and hexagonal ZnS with copper activator in proportions from zero to 3000 parts per million, (2) a direct proof for ZnS-type phosphors of the equation of trap emptying proposed by Randall and Wilkins, (3) a detailed extension of the study of retrapping by the method indicated by Wilkins and Garlick, (4) a determination of the number of electron traps in ZnS as a function of heating temperature in preparation, (5) an analysis of glow and decay curves by means of the equation of Randall and Wilkins, and (6) suggestions concerning the identity of traps and luminescence centers on the basis of a study of the crystal structures of cubic and hexagonal ZnS.