Synthesis of Y2O3 nano-powders by precipitation method using various precipitants and preparation of high stability dispersion for backlight unit (BLU)

Nano-sized yttria powder was successfully synthesized by precipitation method. Three different precipitants such as NH4OH, mixture of NH4OH and NH4HCO3, and NH4HCO3 were used. It was observed that the size of yttria powder is significantly affected by type of precipitant depending on the rate of formation of precipitate. It is seen that NaHCO3 shows the most significant pH decrease during the formation of Y2CO3, thus leading to the formation of large crystal. The result also shows that the crystal size depends on calcinations temperature and the agglomeration have become more significant beyond 800 °C where the morphology have changed from flake to spherical shape interconnected each other. It was observed that the dispersity of yttria powder can be affected by bead size of ball mill, rpm and dispersion time where the physical, agglomeration has become more significant beyond 4 h of dispersion. Finally, the nano-sized yttria powder of on the average 114 nm shows excellent uniform coating, sufficient transmittance and excellent brightness for lamp.