Electroluminescent, EL, materials are of interest in providing high brightness for display screens found in portable electronic devices, where the battery life is limited. Currently organic luminescent materials are being used, but the lifetime is low due to the degradation of the organic material under electric field over time. Some recent work with inorganic material of zinc sulfide has indicated high brightness at very long life times. This work focuses on the thermal processing of the zinc sulfide based EL material with trinitrotoluene, TNT. The zinc sulfide based phosphor and TNT are placed in a stainless steel container that can withstand high pressure. After closing, the chamber was evacuated and subsequently heated to over 300°C. The ZnS based phosphor was heated to a high temperature as the TNT decomposed. The sample was recovered after cooling and separated by optical observation of photoluminescence with a ultraviolet lamp. X-ray diffraction analysis showed that some transformation to hexagonal wurtzite phase occurred and was retained after cooling. EL and photoluminescence, PL, measurements were performed to characterize the luminescent properties of the material. Results of SEM observations of the particle sizes are discussed. The most recent data shows that blue luminescence at 450nm can be obtained by the treatment of ZnS phosphor with TNT in this high pressure containment device.