Transport Properties and Thermal Expansion of Sr0.97Ti1−FexO3− (x=0.2–0.8)

Oxygen ionic conduction in brownmillerite CaAl0.5Fe0.5O2.5+

“…The characterization of CaAl 0.5 Fe 0.5 O 2.5 ceramics included also scanning electron microscopy combined with energy dispersive spectroscopy (SEM/EDS), dilatometry, differential thermal and thermogravimetric analysis (DTA/TGA), and the measurements of total conductivity (four-probe DC) and steady-state oxygen permeability. The experimental procedures and equipment used for the characterization were reported elsewhere ( [6,[8][9][10][14][15][16] and references cited). All data on the oxygen permeation presented in this paper correspond to the membrane feed-side oxygen partial pressure (p 2 ) of 21 kPa (atmospheric air); the permeate-side oxygen pressure (p 1 ) varied from 0.8 to 20 kPa.…”

“…The essentially one-dimensional character of the ionic conduction seems to be responsible for the fact that the ionic conductivity of CaAl 0.5 Fe 0.5 O 2.5þd (Fig. 6) is lower than that of Sr 4 Fe 6 O 13þd , where the concentration of ionic charge carriers in air is also low, but the transport is two-dimensional [14]. Note that the ideal perovskite structure presents a threedimensional network of linear diffusion pathways.…”

“…These vacancies were assumed to significantly contribute to ionic transport, forming one-dimensional diffusion pathway for oxygen ion migration in the tetrahedral layers [12,13]. On the contrary, experimental data on partially ordered ferrites [6,11,14] suggest that oxygen-vacancy ordering leads to decreasing ionic conduction. Studying of the ionic transport in brownmillerite-type compounds may therefore provide a better understanding of oxygen diffusion processes in ferrite phases.…”

“…Studying of the ionic transport in brownmillerite-type compounds may therefore provide a better understanding of oxygen diffusion processes in ferrite phases. Continuing our research on Fecontaining mixed conductors [6,8,10,[14][15][16], the present work is focused on the determination of ionic conductivity of brownmillerite CaAl 0.5 Fe 0.5 O 2.5 and on the evaluation of structural factors affecting ion mobility in the brownmillerite lattice.…”

Oxygen permeability of LaGa0.65Ni0.20Mg0.15O3−δ ceramics: effect of synthesis method

“…In particular, perovskite-like solid solutions based on (Sr,La)(Fe,Co)O 3Àd exhibit attractively high oxygen permeation¯uxes, but are thermodynamically and/or dimensionally unstable under large oxygen chemical potential gradients [3±7]. To some extent, the stability of (Sr,La)(Fe,Co)O 3Àd can be improved by partial substitution of the B-site cations with ions having a higher oxidation state, such as Cr [3,5,6] or Ti [5,8]. This type of doping leads, however, to a decrease in the ionic conductivity and oxygen permeability (OP) [8,9].…”