Characteristics of low-voltage behavior for blue ZnS:Ag phosphors coated with SnO2

In this study, the effect of a SnO2-x coating layer on sulfide phosphor powders for CRTs (cathode ray tubes) on the low-voltage luminescence were evaluated. SnO2-x was coated on blue ZnS phosphors by using the uniform precipitation method with SnCl4.4H(2)O through a pH shift in solution by decomposition of ureas. PL (photoluminescence) and CL (cathodoluminescence) were measured for the SnO2-x-coated ZnS:Ag powders, and those results are discussed as they relate to the X-ray diffraction data and the energy band gaps for the materials. The luminescent characters for the ZnS:Ag phosphors depended on the SnO2-x coating content and the heat treatment conditions. The CL intensity for the SnO2-x-coated phosphors were higher than that of as-received sample due to the semiconductivity of the SnO2-x. For example, the 2.5-wt% SnO2-x-coated ZnS:Ag phosphors heat treated at 300 degrees C/2 hr showed a 43 % increase in brightness measured at 1.5 kV and 1 mA compared to as-received phosphors.