This paper focus on the mechanism of zirconium oxidation at 850 degrees C by X-ray diffraction (XRD) and the interactions between chemical (oxide growth, phase proportion) and physical processes (oxide scale texture, mechanical stresses). The structural gradients in the oxide scale composed of monoclinic ZrO2 (higher proportion) and tetragonal ZrO2 were revealed by XRD at variable incidence. The spatial evolution of the monoclinic zirconia texture through the oxide scale was shown and quantified. Relaxation of the oxide compressive stresses was observed for different oxidation times and correlated to kinetic breakaway evidenced by other methods. A structural mechanism of the oxide formation is then proposed, which prove the interest of XRD in the investigations on heterogeneous kinetics.