CHEMICAL SYNTHESIS OF MIXED OXIDE POWDERS FOR SOLID OXIDE FUEL CELL (SOFC) ELECTROLYTE AND ELECTRODES

摘要

Synthesis of LSGM (La_(0.9)Sr_(0.1)Ga_(0.8)Mg_(0.2)O_(3-δ)), LSFM (La_(0.9)Sr_(0.1)Fe_(0.8)Mg_(0.2)O_(3-δ)) and LSCM (La_(0.9)Sr_(0.1)Cr_(0.8)Mg_(0.2)O_(3-δ)) powders were achieved via an organic precursor method. Different organic "carrier" molecules were used for powder synthesis. Citric acid (CA), tartaric acid (TA), Pechini precursors, polyvinyl alcohol, and ethylenediaminetetraacetic acid (EDTA) were selected as organic carriers for their ability to stabilize the metal ions. Each organic carrier material exhibited a different degree of effectiveness in the synthesis of the mixed oxide powders. One of the main factors affecting the phase purity appears to be the interaction of the functional groups with the constituent cations. It was determined that amorphous LSGM first crystallizes at 625°C. However, elimination of undesired phases requires higher temperatures. Possible implications of limited MgO solubility on the ionic conductivity are presented. Impedance measurements as a function of temperature up to 545°C revealed that the x-ray phase pure pellets may have extrapolated ionic conductivity values as high as 0.14-0.16 S/cm at 800°C.