The effect of Gd doping in La1-x-yGdxSryMnO3 compound on nanocrystalline structure by X-ray Absorption Spectroscopy (XAS) technique

This work presents the structural study of La1-x-yGdxSryMnO3 or LGSM compositions where 0 <= x <= 0.15 and 0 <= y <= 0.45, respectively. In particular, the effect of doping Gd concentration and the size mismatch of A-site cations from the substitution of Gd for La on the MnO6 octahedral structure is focused as the average size of the cations occupying in A-site is fixed. The LGSM nanoparticles are carefully studied and analyzed using X-ray diffraction (XRD) and X-ray Absorption Spectroscopy (XAS) including X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS). The XRD results obtained from Rietveld refinement show that all nano-powder samples have rhombohedral structure. From the XANES technique we found that the effect of Gd substitutions causes the slight increase of mean oxidation state of Mn from 3.50 to 3.65. Furthermore, the results of MnO6 octahedral analysis obtained from EXAFS technique show that the local structure around Mn atoms for LG05 and LG10 samples can be explained by 4(s) + 2(I) model while the LG15 sample can be explained by 6 model. (C) 2015 Elsevier B.V. All rights reserved.