Electrical conductivity of iron-doped calcium titanate

Both total and partial electronic conductivity of iron-doped calcium titanates, of general formula CaTi1-xFexO3-delta (x = 0, 0.1,...0.5), were investigated as a function of oxygen partial pressure at high temperatures (900, 1000 degrees C) by means of the four-probe technique and the Hebb-Wagner polarization method, respectively. The oxygen partial pressure interval extended from 1 to 10(-18) atm. Ti substitution by Fe results in a considerable increase of both ionic and electronic conductivity and in appearance of a wide region of primarily ionic conductivity, independent of the oxygen partial pressure. Of these compositions, the x = 0.2 sample has the highest oxygen ion conductivity. A model of defect equilibrium is discussed. (C) 1999 Elsevier Science BN. All rights reserved.