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

Abstract La 0.7 Sr 0.3 Cr 0.4 Mn 0.6 O 3-δ perovskite nanoparticles have been synthetized using an ethylene glycol modified sol-gel method and impregnated by Cu 0.75 Ni 0.25 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 0.7 Sr 0.3 Cr 0.4 Mn 0.6 O 3-δ and SrCrO 4 solid solutions with Pm 3 ¯ m cubic and P 2 1 /n monoclinic symmetry respectively in the range of 600–650 °C. Symmetry reduction from the Pm 3 ¯ m ⟶ R 3 ¯ 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 [ 2 2 1 ] / ( 1 2 2 ) . The Johnson-Mehl-Avrami model had described the whole process, where the existence of two phases was shown before it reached its complete D 3 d 6 point group symmetry.