Ln_(0.6)Sr_(0.4)FeO_(3-δ)(Ln=La、Nd、Ce)阴极材料的制备与表征

Study on preparation and characterization of Ln_(0.6)Sr_(0.4)FeO_(3-δ)(Ln=La,Nd,Ce) for IT-SOFC cathodes

以甘氨酸硝酸盐水溶液为前驱体合成了Sr掺杂的稀土铁酸盐Ln0.6Sr0.4FeO3-δ(Ln=La、Nd、Ce)粉体。对制备过程的化学键变化、样品的热稳定性、物相形成过程及导电性进行了表征。结果表明,甘氨酸硝酸盐合成法成相温度低于1000℃。坯体烧结较粉状样品更有利于钙钛矿物相的形成,La0.6Sr0.4FeO3-δ及Nd0.6Sr0.4FeO3-δ坯体1000℃煅烧2h即可形成近乎单一的钙钛矿相(ABO3);Ce0.6Sr0.4FeO3-δ是CeO2立方萤石相和产物钙钛矿相共存,两相难分主次。合成样品低温下的导电行为符合小极化子导电机制;1200℃烧结的La0.6Sr0.4FeO3-δ样品在测试全温度范围内(450～800℃)电导率超过100S/cm,Nd0.6Sr0.4FeO3-δ在中温区(600～800℃)电导率>60S/cm;Ce0.6Sr0.4FeO3-δ样品的电导率不理想。

Ln0.6Sr0.4FeO3-δ(Ln=La, Nd, Ce) composite oxides with Sr doped at A-site were prepared using glycine-nitrate aqueous solution as precursors. The structure and preparation process were analyzed by means of FT-IR and TG-DTA and X-ray diffractometer. The electrical conductivities of samples were determined by DC four-probe technique. The results showed that the temperature of forming structure is lower than 1000°C, the perovskite-type phase of products has obtained at the moment of ignition. The Ln0.6Sr0.4FeO3-δ wafer is almost a single perovskite-type phase after sintered at 1000°C for 2h, while the powder exhibits impure peaks after sintered at 1400°C for 4 h, which implies material state has an important effects on phase forming. Two phases with fluorite and perovskite phase presents in Ln0.6Sr0.4FeO3-δ. The electrical conductivity certified that the hopping of small polaron is the dominating mechanism at low temperature. Both of the Ln0.6Sr0.4FeO3-δ and Ln0.6Sr0.4FeO3-δ, the electrical conductivity was over 60 S/cm, and that of the Ln0.6Sr0.4FeO3-δ sample sintered at 1200°C for 2h was over 100 S/cm in the range of 450-800°C. The electrical property of Ln0.6Sr0.4FeO3-δ was disillusionary.