Single phase PbTiO3 thin films were synthesized by thermal treatment at temperatures 350-700 degreesC of Pb/Ti magnetron sputtered layered structures at atmospheric pressure in air. The film stoichiometry was accurately controlled by deposition of individual layers with the required thickness. Scanning electron microscopy views showed that initially smooth surfaces had porous and granular structure after thermal annealing. Surface morphology depends on the substrate material and the cooling rate. X-Ray diffraction patterns revealed the nanometric microstructure of synthesized films. The size of crystallites in oxidized films depends on the annealing temperature and does not depend on the annealing time. The atomic mixing and oxidation kinetics are discussed and applied to PbTiO3. The emphasis is made on the analysis of surface atom relocation and restructuring processes under reactive adsorption at elevated temperatures and their role in the formation of surface instabilities and initiation of transport of oxygen from the surface into the bulk directed to stabilize these instabilities. The experimental results support that the formation of PbTiO3 films homogeneous in structure and composition during the thermal oxidation is a result of intensive mixing of Pb/Ti layers with continuous supply of oxygen though the surface. Under non-equilibrium conditions on the surface, the oxygen atoms are driven into grain boundaries of crystallites, result in high compressive stress inducing fragmentation of grains and their oxidation by oxygen diffusion through boundaries into the nanograins. The oxidation kinetics and the size of crystallites is governed by the mass-transport processes.