Synthesis and Characterization of Praseodymium Cuprates Compounds as Innovative and Efficient Oxygen Electrode for IT-SOFCs

摘要

The peculiar structure of PrBa_2Cu_3O_(6+δ) (Pr123) consists of Pr-O, Cu~(2+) chains (CN = 4) and Cu~(3+) pyramidal (CN = 5) layers, regularly alternated along the c axis. Different issues related to material instability were investigated producing samples with identical composition, but with different thermal history. Rietveld refinements revealed the compresence of two Pr123 phases: a tetragonal one (Pr123-T), stable at high temperatures, and an orthorhombic phase (Pr123-O), resulting from the oxidation of Pr123-T below 750-700°C. The Pr123 samples produced with different cooling rates showed that different O/T ratios influence the oxygen content (6+δ), the electrical conductivity and the polarization resistances. EIS tests were performed on symmetrical electrolyte supported cells with Pr_(0.3)Ce_(0.7)O_(2-δ) (PrDC30) interlayer, starting the measurements at 500°C, then increasing up to 700°C. Promising ASR values were obtained for these compounds, with different activation energies, which indicated different ORR mechanisms.