中温固体氧化物燃料电池阴极材料La_(0.7)Sr_(0.2)Ca_(0.1)Co_(1-x)Fe_xO_(3-δ)的合成与导电性能

Synthesis and Conductivity of La_(0.7)Sr_(0.2)Ca_(0.1)Co_(1-x)Fe_xO_(3-δ) as A Cathode Material for IT-SOFC

采用固相反应法合成了锶、钙与铁掺杂的稀土复合氧化物La0.7Sr0.2Ca0.1Co1-xFexO3-δ(x=0.3,0.5);通过TG-DTA分析了产物的形成过程;分别测试了产物在100～900℃间的混合电导率和热膨胀系数;对产物的晶体结构与晶粒形貌等进行了表征。结果表明:经1 200℃烧结后的两种产物均具有单一的菱方钙钛矿结构;晶粒生长情况较好,但尺寸不够均匀;混合电导率随温度升高先升后降,在600～800℃均大于100 S.cm-1,可满足要求,在100～500℃与温度基本保持线性关系,其导电行为符合小极化子导电机理;钙与铁同时掺杂有效降低其热膨胀系数,表明钙钛矿晶格的热稳定性得以提高。

Rare earth composite oxides La0.7Sr0.2Ca0.1Co1-xFexO3-δ（x=0.3,0.5） doped with Sr,Ca and Fe were synthesized by solid state reaction.The forming process of the products was analyzed by TG-DTA testing.The mixed conductivity and thermal expansion coefficient（TEC） of the products were measured in 100-900 ℃.The crystal structure and grain morphology of the products were characterized.The results show that both the two oxides had a single rhombohedral perovskite structure,and the grain growth was good,but the size was not uniform enough after sintering at 1 200 ℃.The mixed electrical conductivity increased first and then decreased with the increase of temperature.The conductivity of the two oxides was larger than 100 S·cm-1 at 600-800 ℃ which could meet the demand.The conductivity kept linear relation with the temperature which showed that the conductive behavior accorded with the small-polaron conductive mechanism at 100-500 ℃.Ca and Fe doping at the same time could effectively reduce the TEC which indicated that the thermal-stability of the perovskite lattice increased.