Preparation of fine silver powder from silver phosphate by direct electro-reduction

Fine silver powder was prepared by direct electro-reduction of chemically precipitated silver phosphate powder. The Ag3PO4 powder was in the form of aggregates of small particles around 1 μm in size. The charge consumed during the electro-reduction agreed well with the predicted theoretical reaction. The phase conversion ratio of 99.8% was verified by X-ray diffraction analysis and inductively coupled plasma spectrometry. The shape of the Ag3PO4 powder particles was preserved during electro-reduction at room temperature, but their size was reduced. Electro-reduction of the Ag3PO4 powder at 60 °C exhibiting increased solubility led to an appreciable change in the shape of the electro-reduced silver powder particles. The electro-reduction process may proceed via a solid-state reaction with two reaction paths, indicated by different potentials.