Redox transitions in strontium vanadates: Electrical conductivity and dimensional changes

Abstract

The reversibility of redox-induced phase transformations and accompanying electrical conductivity and dimensional changes in perovskite-type SrVO3-delta, a parent material for a family of potential solid oxide fuel cell anode materials, were evaluated employing X-ray diffraction, thermal analysis, dilatometry and electrical measurements. At 873-1273 K, the electrical conductivity of SrVO3-delta is metallic-like and 6-8 orders of magnitude higher compared to semiconducting V5+-based strontium pyrovanadate Sr2V2O7 and strontium orthovanadate Sr3V2O8 existing under oxidizing conditions. SrVO3-delta is easily oxidized to a pyrovanadate phase at atmospheric oxygen pressure. Inverse reduction in 10%H-2-90%N-2 atmosphere occurs in two steps through (5Sr(3)V(2)O(8) + SrV6O11) intermediate. As Sr3V2O8 is relatively stable even under reducing conditions, the perovskite phase and its high level of electrical conductivity cannot be recovered completely in a reasonable time span at temperatures Sr2V2O7 redox transformation is accompanied with significant dimensional changes. Their extent depends on the degree of phase conversion and, apparently, on microstructural features. (C) 2014 Elsevier B.V. All rights reserved