Study of mechanism of mixed conduction due to electrons and oxygen ions in (La0.75SrO0.25)MnO3.00 and (Ba 0.5Sr0.5)(Co0.8Fe0.2)O 2.33 through Rietveld refinement and MEM analysis

Abstract

In this study, we have analyzed the mechanism of mixed conduction due to electrons and oxygen ions in (La0.75Sr0.25)MnO 3.00 (LSM) and (Ba0.5Sr0.5)(Co 0.8Fe0.2)O2.33 (BSCF) by using the Rietveld refinement technique and the maximum entropy method (MEM). Using neutron diffraction measurements, we showed that the site occupancies of the O1 (4c) and 02 (8d) sites in BSCF are 0.59 and 0.87, respectively. Further, the MEM analysis of synchrotron X-ray diffraction measurements revealed that the Mn-O plane in LSM has a strong, isotropic covalent bond that enables conduction of electrons. The (Co, Fe)-O2 plane with a covalent bond and a low concentration of oxygen vacancies in BSCF can also conduct electrons. On the other hand, the (Ba, Sr)-O1 plane in BSCF, which has a high concentration of oxygen vacancies, large isotropic displacement parameter (Uiso) values, and a strong ionic bond, is responsible for the diffusion of oxygen ions.