Effects of Reaction Conditions on the Properties of Spherical Silver Powders Synthesized by Reduction of an Organometallic Compound

Silver powders were synthesized by reducing a silver organometallic compound, silver 2-ethylhexanoate, with di-n-octylamine. The effects of preparation conditions on the characteristics of the powders were investigated. Silver powders prepared from silver 2-ethylhexanoate and di-n-octylamine in the ratio 2:1 (MA21) at 150°C for 3 h had the best characteristics (average particle size 277 nm, narrow particle-size distribution, high tap density of 4.0 g/cm³), and were also obtained in high yield (98%). Use of an excessive amount of di-n-octylamine resulted in intense thermolysis and a low yield of silver powders of irregular morphology with a wide particle-size distribution. As the proportion of silver 2-ethylhexanoate was increased, the silver powders obtained had a bimodal particle-size distribution and a relatively low tap density. Silver films seemed to have high resistivity when the temperature used for synthesis of the silver powders was too low or reaction time was insufficient. The electrical resistivities of silver films prepared from MA21 powders and sintered at 300°C and 500°C for 30 min were 3.8 × 10^?6 Ω cm and 2.3 × 10^?6 Ω cm, respectively, close to that of bulk silver.