XANES Study of La0.75-xGdxCa0.25MnO3-δ Solid Solutions

V.A. Drozda, c, M. Pęka̶ab, R.S. Liu c, J.-F. Leed and J.M. Chen d aDepartment of Chemistry, Kiev National Taras Shevchenko University, 60 Volodymyrska, Kiev, 01033 Ukraine; bDepartment of Chemistry, Warsaw University,Żwirki i Wigury 101, Warsaw, Poland cDepartment of Chemistry, National Taiwan University, Roosevelt Road, Section 4, Taipei 106, Taiwan, ROC dNational Synchrotron Radiation Research Centre, Hsinchu 300, Taiwan, ROC

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Received: 25 09 2005;

A series of solid solutions La0. 75-xGdxCa0.25MnO3-δ with 0.0≤x≤0.75 was prepared via carbonate precursor precipitation method. Final sintering was performed at 1250ºC in oxygen flow atmosphere. The samples obtained were characterized by scanning electron microscope, X-ray diffraction measurements. Oxygen stoichiometry was analyzed by iodometric titration method. X-ray absorption spectroscopic methods of Mn L-edge and Mn K-edge X-ray absorption near edge structure were used to study oxidation state of manganese in the solid solutions and elucidate features of their local crystal structure. Orthorhombic crystal structure characteristics of the solid solutions were refined by Rietveld method. An increase in oxygen deficiency and average manganese oxidation state were found to accompany Gd concentration increase in La0.75-xGdxCa0.25MnO3-&3948;. These results are consistent with Mn L-edge X-ray absorption near edge structure spectra, where a gradual change of Mn oxidation state with Gd concentration increase was detected. Origins of oxygen deficiency La0.75- xGdxCa0.25MnO3-δ are discussed in terms of structural disorder caused by Gd substitution for La.

DOI: 10.12693/APhysPolA.109.583 PACS numbers: 75.47.Lx, 61.10.Ht