Abstract: According to the principles of simultaneous equilibrium and mass balance, a series of thermodynamic equilibrium equations of system at ambient temperature were deduced theoretically and the logarithm concentration versus pH value (lg[Cu2+]T—pH) diagrams at different solution compositions were drawn. The results show that when pH is below 5.0, copper ion reacts with directly and the morphology of copper precursor powder is of pie-shape; when pH is above 5.0, copper ion coordinates with ammonia, and the precipitation proceeds slowly accompanying with the release of copper ions from the multi-coordinated (n =1, 2, ∙∙∙, 5) and the morphologies of copper precursor powder are respectively of rod aggregation shape (when 5.0＜pH＜8.0) and of rod-shape (when pH＞8.0). Some experiments were performed to confirm the relation between the total concentration of copper ion and pH value. It is shown that the thermodynamic mathematical model is correct and the calculated values are basically accurate.

Key words: thermodynamic equilibrium; copper oxalate precursor; ultrafine copper powder; morphology