A homogeneous and stoichiometric Pb(Zr,Ti)O ₃ (PZT) fine powder was prepared by thermal decomposition of the metal oxalate precursor formed by the precipitation reaction of the metallic components in aqueous solution with oxalic acid. Theoretical solubility isotherms of metal oxalates were established as a function of the solution pH and the metal ion concentration using thermodynamic equilibrium constants for the corresponding metal salts in aqueous solution. Through the theoretical solubility isotherms, the optimum pH domain for preparing the homogeneous and stoichiometric PZT–oxalate precursor was found to be 3–4. Crystalline PZT with tetragonal symmetry began to form after heating the precursor at 600 °C and a monophasic PZT powder consisting of submicrometer (0.3–0.5 µm) particles with spherical shape could be obtained after calcination at 800 °C for 2 h. The oxalate-derived PZT powder showed a good sinterability even below 1150 °C where the piezoelectric properties were optimized.