The mixed silver-copper oxide, Ag2Cu2O4 has been previously synthesized by electrochemical oxidation of suspensions of the precursor Ag2Cu2O3 and also by direct oxidation/coprecipitation of soluble salts. This work shows how the transformation from Ag2Cu2O3 to Ag 2Cu2O4 can take place in solid state at room temperature by ozonization of the precursor. The final phase is overstoichiometric in oxygen but shows the same structural features of the firstly described phase Ag2Cu2O4. The maximum content of oxygen achieved is 4.34 per unit formula. © 2004 Elsevier Inc. All rights reserved.