Transport Properties and Themral Expansion of Sr_(0.97)Ti_(1-x)Fe_xO_(3-#delta#) (x=0.2-0.8)

摘要

Increasing iron concentration in perovskite-type solid solu- lions Sro.97Til-xFexO3-.1 (x = 0.2-0.8) was found to decrease the unit cell volume and to increase the partial ionic and electronic conductivities as well as the thermal expansion. The oxygen permeation through Sro.97(Ti,Fe)O3-.1 membranes is limited by both bulk ionic conduction and surface exchange rates. pro- longed stabilization under oxygen chemical potential gradients suggests formation of ordered microdomains in the perovskite lattice. The activation energy for the ionic conductivity, evalu- ated from oxygen permeation and Faradaic efficiency data, is nearly independent of iron content, varying in the range 97-104 kJ /mol. Thermal expansion coefficients of SrO.97 Til_xFex 03-.1 (0: = 0.4-0.8) vary from (11.7-13.8)x 10-6 K-1 at temper- atures of 300-720 K to (16.6-27.0) x 10-6 K-1 at higher temper- atures. In comparison with the Sr(Ti, CO)O3-.1 system, strontium titanates ferrites possess somewhat poorer transport properties, but lower thermal expansion.