材料期刊网

La0.7Sr0.3Cr0.4Mn0.6O3-δ perovskite nanoparticles have been synthetized using an ethylene glycol modified solgel method and impregnated by Cu0.7sNi0.25 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 ℃.Nanoparticles with crystal size < 26 nm start through nuclei formation of La0.7Sr0.3Cr0.4Mn0.6O3.δ and SrCrO4 solid solutions with Pm(3)m cubic and P21/n monoclinic symmetry respectively in the range of 600650 ℃.Symmetry reduction from the Pm(3)m→R(3)c space group had been obtained at a lower temperature (750 ℃) 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)l]/(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 D63d point group symmetry.