H.I. Won

Highly effective synthesis and photoluminescence of Sr2Si5N8:Eu2+ red-emitting phosphor for LEDs.

We developed a highly effective and self-sustaining route for synthesizing Sr(2)Si(5)N(8):Eu(2+) red-emitting phosphor particles for use in light emitting diodes (LEDs). The phosphors thus synthesized showed excellent emission characteristics under a blue excitation wavelength of 450 nm, had a uniform particle size distribution, and showed high performance in LED packages.

Synthesis of ZnS Phosphor Particles in Exothermic Frontal Waves

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.

Synthesis of Sr 3 Al 2 O 6 Phosphors by Solid State Reaction and Its Luminescent Properties

A red strontium aluminate phosphor (Sr₃Al₂O?:Eu³?, Eu²?) is synthesized using a solid state reaction method in air and reducing atmosphere. The investigation of firing temperature indicates that a single phase of Sr₃Al₂O? is formed when the firing temperature is higher than 1300℃. The effect of firing temperature and doping concentration on luminescent properties are investigated. Sr₃Al₂O? phosphor exhibits the typical red luminescent properties of Eu³? and Eu²?.

The laws of silicon ingot formation by combustion reaction

The formation of a phase pure silicon ingot from SiO2+Al+KClO3 and Na2SiO3+Al+KClO3 systems was investigated thermodynamically and experimentally under combustion mode, known also as self-propagating high-temperature synthesis (SHS). The regularities of combustion and phase formation versus KClO3 concentration by a thermocouple technique were obtained. The morphology, chemical and phase composition of the silicon ingot were analyzed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and ICP-analysis. The method reported here proved effective in producing silicon ingots with a purity of 98%.