Relationship among the local structure, chemical state of Fe ions in Fe-O polyhedra, and electrical conductivity of cubic perovskite Ba_(1-x)Sr_xFe_(0.9)In_(0.1)O_(3-δ) with varying number of oxide ion vacancies

摘要

Cubic perovskite oxide Ba1-xSrxFe0.9In0.1O3-delta (BSFI) with varying number of oxide ion vacancies was prepared by heating in N-2 and O-2 to elucidate the relationship among the local structure of Fe-O polyhedra, the chemical state of Fe ions, and their electrical conductivities. MOssbauer spectroscopy for the N-2-heated specimens (BSFI-N-2) showed that the volume of microdomains in which the Fe-O-Fe super-exchange interaction worked well increased as the Sr content increased, resulting in reduced activation energy of the small-polaron hopping. It was found that as the Sr content increased, the increase in the mobility of small polamns enhanced the electrical conductivity in BSFI-N-2. Further, it was found that the increase in the number of the charge carriers and the small-polamn mobility enhanced the electrical conductivity of the O-2-heated specimens (BSFI-O-2) with increasing x.