Internal pressure effect on cathodoluminescence enhancement of ZnS:Mn²⁺synthesized by a sealed vessel

ZnS:Mn²⁺phosphors were synthesized by a modified solid-state reaction method. In the synthesis method, a sealed vessel is used, where heat and pressure are simultaneously utilized. The effects of various synthesis conditions such as temperature, Mn concentration, and pressure on the cathodoluminescence (CL) were investigated. Among them, pressure had an effect on CL property as much as others. It was observed that CL intensities of ZnS:Mn²⁺phosphors increased with the increase of pressure and the best sample showed higher intensity than that of a commercial one by 180%. X-ray diffraction (XRD) and electron paramagnetic-resonance (EPR) were used to understand the enhancement. No change of XRD patterns was observed but the full width at half-maximum (FWHM) of the most intense cubic (111) peak of ZnS:Mn²⁺decreased with the increase of pressure. EPR signal intensity of Mn²⁺increased with the increase of pressure. The improved crystallinity and more substitution of Zn²⁺with Mn metal were believed to be responsible for the enhancement.