Improvement of electrical conductivity of La0.3Sr0.7Co0.9Fe0.1O3 perovskites for solid oxide fuel cell

Abstract

The electrical conductivity and oxygen permeation of Ca2+, Zn2+ and Mg2+-doped La0.3Sr0.7Co0.9Fe0.1O3 (LSCF) were investigated. The synthesized materials were characterized by XRD, XPS and XAS. LSCFs were synthesized by modified citrate method and studied for the effect of sintering temperature. LSCF sintered at 1200 oC showed the higher oxygen permeation rate and more idealized cubic structure than others. By replacing La3+ and Sr2+ ions of LSCF with Ca2+ ions, La0.3Sr0.7-xCax Co0.9Fe0.1O3 (X = 0 - 0.7) and (La0.3Sr0.7)1-xCaxCo0.9 Fe0.1O3 (X = 0 - 0.4) were successfully synthesized. La0.3Sr0.7-xCaxCo0.9Fe0.1O3 showed pure perovskite phase with primitive cubic form when X = 0 - 0.5 whereas (La0.3Sr0.7)1-xCaxCo0.9Fe0.1O3 exhibited pure perovskite phase with primitive cubic and tetragonal forms when X = 0-0.2 and X = 0.3 - 0.4, respectively. La0.3Sr0.5Ca0.2Co0.9Fe0.1O3 showed the highest electrical conductivity in this work due to a lot of IS Co4+ and HS Co3+. To improve oxygen permeation of La0.3Sr0.5Ca0.2Co0.9Fe0.1O3, Co3+ and Fe3+ ions were replaced with Zn2+ and Mg2+ ions to obtain La0.3Sr0.5Ca0.2Co0.9-yMyFe0.1O3 and La0.3Sr0.5Ca0.2(Co0.9Fe0.1)1-y MyO3 (M = Zn2+, Mg2+, Y = 0 - 0.05). Only La0.3Sr0.5Ca0.2Co0.9-yZnyFe0.1O3 (Y = 0 - 0.03) were achieved as pure perovskite phase with primitive cubic structure. The oxygen permeation rate was increased with increasing Zn2+ content because high spin Co2+,3+ and oxygen vacancies were increased.