Nucleation and growth kinetics of La0.7Sr0.3Cr0.4Mn0.6O3-δ SOFC perovskite: Symmetry alteration evolution induced by Cu2+ and Ni2+ impregnation

La0.7Sr0.3Cr0.4Mn0.6O3-δ perovskite nanoparticles have been synthetized using an ethylene glycol modified sol-gel method and impregnated by Cu0.75Ni0.25 nanoparticles. The phase transitions and nucleation kinetics were studied by time resolved x-ray diffraction, Rietveld, Raman spectroscopy and high resolution transmission electron microscopy. Findings have shown that, an atomic disorder dominates from room temperature to 400 °C. Nanoparticles with crystal size <26 nm start through nuclei formation of La0.7Sr0.3Cr0.4Mn0.6O3-δ and SrCrO4 solid solutions with Pm3¯m cubic and P21/n monoclinic symmetry respectively in the range of 600-650 °C. Symmetry reduction from the Pm3¯m⟶R3¯c space group had been obtained at a lower temperature (750 °C) than those reported in the literature in oxygen atmosphere and it was confirmed by an octahedral distortion, which takes place in the crystallographic direction[22̅1]/(12̅2). The Johnson-Mehl-Avrami model had described the whole process, where the existence of two phases was shown before it reached its complete D3d6 point group symmetry.