La0.6Sr0.4Co1-yFeyO3系阴极材料的有机凝胶法合成与电性能

采用有机凝胶法合成了中温固体氧化物燃料电池（IT-SOFCs）阴极材料La0.6Sr0.4Co1-yFeyO3（LSCF）,通过TG-DTA,XRD研究了凝胶前驱体的热分解及其相转化过程,使用直流四引线法测量了烧结体的电导率,并初步探讨了电输运机制.结果表明：凝胶前驱体在850℃焙烧2 h可以形成颗粒细小（约20 nm）、完全晶化的纳米粉体;所有LSCF烧结体的电导率随温度的升高基本上都呈先增大后减小的趋势,并在650-750℃之间达到最大值,中低温段的电导率随温度的变化符合小极化子导电机理.在相同温度下,随着Co/Fe比例的增加,LSCF烧结体的电导率增大,中低温区域内的表观活化能下降.在700℃时,La0.6Sr0.4Co1-yFeyO3陶瓷的电子电导率在195-792 S.cm^-1之间,完全能够满足IT-SOFCs的要求.

Synthesis and electrical properties of La0.6Sr0.4Co1-yFeyO3 cathode materials by organic gel method

The single phase La0.6 Sr0.4 Co1-y FeyO3 （LSCF, y = 0.2, 0. 8） cathode materials for the intermediate temperature solid oxide fuel cells （IT-SOFCs） were synthesized by organic gel method. The thermal decomposition and phase inversion process of the gel precursors were studied by thermogravimetric and differential thermal analysis （TG-DTA） and X-ray diffraction （XRD）. Moreover, the electrical conductivities of sintered ceramics were measured by the standard direct current four-wire method, and the mechanism of electronic transport was investigated. The results show that well-crystallized powders with fine crystalline grain （ -20 nm） can be ob- tained after the gel precursors are calcined at 850 ℃for 2 h. The electrical conductivities of all LSCF ceramics increase initially with increasing temperature, reach the maximum values in the range of 650 -750℃, and then decrease. Their electronic transport behavior in medium-low temperature region accords with the small polaron hopping mechanism. The electrical conductivities of LSCF ceramics enhance with the increase of Co/Fe ratio un- der the same measuring temperature, whereas the apparent activation energies of LSCF ceramics decrease with the increase of Co/Fe ratio. The electrical conductivities of LSCF ceramics range from 195 to 792 S·cm-1 at 700℃, which can meet the demand of the electrical properties for the cathode materials in IT-SOFCs.