Zinc silicates are important in CRTs and lamp phosphors. Previous work has shown that a sol-gel-like method (termed CGUPS) can produce uniform zinc silicate phosphor particles whose surface layer possesses an appropriate activator concentration gradient and exhibits efficient cathodoluminescence (CL). This work further investigates this synthesis method in detail and verifies quantitatively the processing parameters for yielding optimal phosphors. Phosphors are evaluated as a function of starting silicic acid particle size ranges and activator (Mn) and coactivator (As) concentrations. Our results indicate that the CGUPS synthesis is not very sensitive to the processing parameters within their initially defined ranges. This study also demonstrates that the CL efficiency of phosphors does depend on particle size and is maximum for 4–7 and 7–12 μm size range with 10 keV electron excitation. For optimal CL efficiency and persistance, the Mn concentration is found to be 0.3% in terms of Mn/Zn ratio and the As/Mn ratio is 36%. © 1989, The Electrochemical Society, Inc. All rights reserved.