Particles in different states of oxidation were prepared by spray pyrolyses of aqueous solutions of silver and copper nitrates under different gas environments: air, nitrogen or mixture gas of 10 vol%H2-N2, respectively. Silver nitrate was converted to phase-pure silver at temperatures below 500 ℃ whose densification and crystallization were completed around 500 ℃, irrespective of the gas environment. On the other hand, phase-pure copper(II) oxide was formed from copper nitrate up to 1,000 ℃ with air, but below 800 ℃ with nitrogen, above which copper(I) oxide was produced. Phase-pure copper particles were obtained with the mixture gas at temperatures above 400 ℃. Copper(I) oxide was sintered and crystallized more easily than copper(II) oxide. The rates of the metallization, sintering and crystallization of copper were between those of silver and nickel.