Abstract
Gallium nitride (GaN) nanopowder used as a blue fluorescent material was synthesized by using a direct current (DC) non-transferred arc plasma. Gallium nitrate hydrate (Ga(NO&sub3;)&sub3;∙xH&sub2;O) was used as a raw material and NH&sub3; gas was used as a nitridation source. Additionally, melamine (C&sub3;H₆N₆) powder was injected into the plasma flame to prevent the oxidation of gallium to gallium oxide (Ga&sub2;O&sub3;). Argon thermal plasma was applied to synthesize GaN nanopowder. The synthesized GaN nanopowder by thermal plasma has low crystallinity and purity. It was improved to relatively high crystallinity and purity by annealing. The crystallinity is enhanced by the thermal treatment and the purity was increased by the elimination of residual C&sub3;H₆N₆. The combined process of thermal plasma and annealing was appropriate for synthesizing crystalline GaN nanopowder. The annealing process after the plasma synthesis of GaN nanopowder eliminated residual contamination and enhanced the crystallinity of GaN nanopowder. As a result, crystalline GaN nanopowder which has an average particle size of 30 nm was synthesized by the combination of thermal plasma treatment and annealing.