Synthesis of Y 2O 3 nano-powders by precipitation method using various precipitants and preparation of high stability dispersion for backlight unit (BLU)

Abstract

Nano-sized yttria powder was successfully synthesized by precipitation method. Three different precipitants such as NH 4OH, mixture of NH 4OH and NH 4HCO 3, and NH 4HCO 3 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 NaHCO 3 shows the most significant pH decrease during the formation of Y 2CO 3, 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.