Surface properties of ZnS and AC powder electroluminescent phosphors

— Phosphor surface properties play an important role in luminescent and processing performance. We studied the distribution of surface active absorption centers (DAC) of ZnS powders and ZnS:Cu electroluminescent phosphors with changes in synthesis and processing conditions. Photometric measurements of the colorimetric indicator adsorption from water solutions demonstrated that in the process of ZnS milling, increasing numbers of active centers are accompanied by the transformation of strong‐acidic centers into weaker ones while moderately basic centers are changed into weaker bases. For the case of phosphor powders, the total number of active centers is inversely related to the intensity of photoluminescence and electroluminescence. This may be explained by considering these centers to be sites of non‐emissive recombinations. Samples with different copper content that distinguished surface centers were studied. It was further found that electron‐beam irradiation causes the formation of strong‐acidic and strong‐basic centers on phosphor surfaces. The DAC acid‐base indicator technique is a useful tool to investigate interfacial processes and surfactant efficiency during phosphor‐based device fabrication.