Synthesis of ZnS Phosphor Particles in Exothermic Frontal Waves

Abstract

In this study, temperature profiles and combustion velocities of a Zn + S system in the presence of sodium halide (SH) as an inert diluent were investigated by combining combustion experiments with the thermocouple measurement technique. Flammability limits were determined experimentally by determining the limiting concentrations of sodium halides for which combustion can be initiated and propagated throughout the reaction pellet. The limiting concentration of NaCl was found to be higher than those of NaF and NaI, indicating that NaCl might be a more effective diluent for the Zn + S system. All reaction mixtures were characterized by low combustion temperature in the range 800–1350 °C and burning velocities in the range of 0.024–0.095 cm/s. Depending on the combustion temperature, this synthetic route provides single-phase modified zinc sulfide powders of sphalerite and wurtzite. ZnS samples doped with halogen ions (H^–) produced sky-blue emission (470 nm) under 340 nm excitation. ZnS samples codoped with Mn²⁺ ions showed a red shift (588 nm) under 356 nm excitation. The relative emission intensity of ZnS:Mn²⁺ phosphor increased as much as 3 times in the NaF → NaI → NaCl range.

Keywords:

• Combustion synthesis
• Exothermal waves
• Luminescence
• Temperature distributions
• Zinc sulfide

ACKNOWLEDGMENTS

This work was financially supported by the research fund of Chungnam National University in 2009.