The Stability and Ionic Conductivity in Cr Doped Y2Ti2O7 in the Search for Potential SOFC Electrolyte Materials

In this study, a series of Y2Ti2-xCrxO7 were synthesized by sol-gel method and characterized by powder X-ray diffraction (PXRD), scanning electron microscope energy dispersive spectroscopy (SEM-EDS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), temperature-programmed reduction (TPR), and AC-impedance to investigate their properties for the application of intermediate temperature solid oxide fuel cell (IT-SOFC). Y2Ti2-xCrxO7 existed single-phase in a range of 0 < x <= 0.8. The refined cell parameters decreased as the amount of doped Cr concentration increased. In addition, the TPR profiles showed that the as-prepared materials started to react with hydrogen in the temperature range of 350 - 450 degrees C. The analyzed results of XPS suggested that the average oxidation state of Cr decreased with the increased Cr content. Measurements of ionic conductivities induced that the optimized performance was observed at x = 0.2 with 0.01 S/cm at 700 degrees C due to an optimized condition of carrier concentration and carrier mobility. The ionic conductivity dropped under reducing condition, indicative of a p-type semiconductor. The as-prepared Y2Ti1.8Cr0.2O7 exhibits low electrical conductivity (0.0004 S/cm at 700 degrees C) and good ionic conductivity, which is potentially suitable to be utilized as an electrolyte material for IT-SOFC.