High-temperature electrical conductivity of Sr0.7La0.3FeO3-delta

The electrical properties of the lanthanum-doped strontium ferrite Sr0.7La0 .3FeO3-delta are studied within the temperature range 750-950 degreesC and the oxygen partial pressure range between 10(-19) and 0.5 atm. The ferrite undergoes a transition from perovskite-like to brownmillerite-like structur e at an oxygen pressure of about 10(-4) atm in the studied temperature rang e. The observed pressure and temperature dependencies of the conductivity i n the browmillerite-like form of the ferrite are related to the transition of the electron conductivity from the intrinsic regime, which is governed b y the band gap of about 2 eV, to the extrinsic regime, which is controlled by the extra-stoichiometric oxygen in the brownmillerite-like phase. The br ownmillerite-like phase is shown to be a mixed conductor with the oxygen co nductivity level rising to about 0.3 S/cm at about 900 degreesC. (C) 2001 E lsevier Science B.V. All rights reserved.