SOFCs阴极材料La_(0.6)Sr_(0.4)Co_(1-x) Fe_x O_(3-δ)溶胶凝胶自燃烧法的制备

Sol-gel auto-combustion synthesis of La_(0.6)Sr_(0.4)Co_(1-x)Fe_xO_(3-δ)cathode materials for SOFCs

以分析纯La(NO_3)_3·6H_2为O、Sr(NO_3)_2、Co(NO_3)_2·6H_2O和Fe(NO_3)_1·9H_2O为原料,采用溶胶凝胶-自燃烧法制备了不同组成的La_(0.6)Sr_(0.4)Co_(1-x)Fe_xO_(3-δ)(LSCF)超细粉体。采用X线衍射(XRD)和透射电子显微镜(TEM)对合成超细粉体的结构和形貌进行测定和表征。结果表明:溶胶凝胶-自燃烧法可一步合成粒径为30～70 nm的LSCF超细粉体,且随着Fe^(3+)含量的增加,衍射峰值向低角度方向略有偏移。对超细粉体的烧结性能、热膨胀性能及电性能进行测试,结果表明:该粉体在1 100℃下烧结2 h,其相对密度达到97%。热膨胀系数随x(Fe^(3+)含量)增加而增大,由x=0.1时的8.42×10^(-6)K^(-1)增大至x=0.5时的9.56×10^(-6)K^(-1)。直流四端子法电导测试表明:电导率随温度的升高(200～800℃)出现极大值,最大值可达950 S/cm,在500～700℃范围内,电导率均在200 S/cm以上,能够很好地满足中低温固体氧化物燃料电池对阴极材料的要求。

Ultrafine La_（0.6）Sr_（0.4）Co_（1-x）Fe_xO_（3-δ）（LSCF） powders were synthesized by a sol-gel auto-combustion method using La（NO_3）_3·6H_2O,Sr（NO_3）_2,Co（NO_3）_2·6H_2O and Fe（NO_3）_3·9H_2O as initial materials. The auto-combustion product structure was characterized by X-ray diffraction（XRD） and transmission electron microscope（TEM）.It was found that the synthesized powder was composed of a single phase with the particle size range from 30 nm to 70 nm and the XRD peaks showed a shift towards low angle as Fe^（3＋） content increased.The ceramic samples sintered at 1100℃for 2 h were found to reach a relative density of 97%.The sintered material had a thermal expansion coefficient of 8.42×10^（-6）～9.56×10^（-6） K^（-1） from x = 0.1 to x =0.5.By the direct current four-probe technique,the measured electrical conductivity increased to a maximum of 950 S/cm with the increased temperature from 200℃to 800℃, and was higher than 200 S/cm from 500℃to 700℃.Thus it meeted the technical requirements for low and intermediate temperature solid oxide fuel cells（SOFCs）.