Abstract: The main technical problems of nickel powder for multiplayer ceramic capacitors are particle size controlling, the agglomeration and tap density. Ultrafine nickel powders with submicron size and spherical shape were synthesized by the hydrazine reduction of nickel sulfate in ethanol-water solvent. The effects of reaction temperature, nucleator and flow rate of nickel sulfate solution on nickel powders properties were investigated. The nickel particles synthesized were characterized by SEM and TGA. The results show that the average particle size changes from 0.1 to 0.7 µm by adjusting reaction temperature (53−73 ℃) and flow rate of nickel sulfate solution (50−100 mL/min). Moreover, temperature below 60 ℃ and appropriate flow rate of nickel sulfate solution (85 mL/min) are in favor of obtaining particles with high tap density (＞3.0 g/cm³). In addition, the introduction of nucleator is useful to obtaining particles with narrow size distribution.

Key words: ultrafine nickel powder; chemical reduction; tap density; multiplayer ceramic capacitor