Method for chemical precipitation of metallic silver powder via a two solution technique

A method for the chemical precipitation of metallic silver powder via a two solution technique, comprising the steps of:

• forming a first solution by dissolving in distilled water an amount of a colloid sufficient to promote formation of particles of a desired size;
• acidifying said first solution by adding an inorganic or organic acid;
• dissolving in said first solution a silver salt;
• adding to said first solution an amount of alumina sufficient to inhibit clumping of particles during precipitation and to retard sintering of particles;
• adding to said first solution an amount of an anionic surfactant sufficient to disperse said alumina during precipitation and to inhibit clumping of particles during precipitation;
• forming a second solution of a tin salt;
• adding said second solution to said first solution to form a precipitation solution in which the ion concentration ratio of silver to tin is approximately 2.0 at a temperature appropriate to effect the chemical precipitation of silver;
• agitating said precipitation solution for a period of time sufficient to precipitate silver powder agglomerates in which from 30% to 80% of the agglomerates have an agglomerate diameter of less than 25 .mu.m, and in which said agglomerates comprise individual powder particles having a diameter of from 0.2 to 2.0 .mu.m;
• and
• heat treating said silver powder particles in air at a temperature ranging from 450 to 750.degree. C.