Effect of concentration of Sm₂O₃ and Yb₂O₃ and synthesizing temperature on electrical and crystal structure of (Bi₂O₃)_1−x−y(Sm₂O₃)_x(Yb₂O₃)_y electrolytes fabricated for IT-SOFCs

For intermediate temperature solid oxide fuel cells (IT-SOFCs), (Bi₂O₃)_1−x−y(Sm₂O₃)_x(Yb₂O₃)_y ternary systems (x=0.01 and y= 0.11), (x=0.05 and y= 0.07), (x=0.07 and y=0.05), and (x=0.11 and y=0.01) as electrolytes have been fabricated at different temperatures (700, 750, and 800 °C) by solid state ceramic technique (SST). The characterization of the samples has been performed by X-ray powder diffractometer (XRD), scanning electron microscopy (SEM), four point-probe method (FPPM), X-ray energy diffraction spectroscopy (EDX), and differential thermal analysis (DTA). XRD measurements have shown that only the samples (Bi₂O₃)_1-x-y(Sm₂O₃)_x(Yb₂O₃)_y (x=0.01, y=0.11 synthesized at 700, 750, and 800 °C) and (x=0.05, y=0.07 synthesized at 800 °C) have stable fluorite type face centered cubic (FCC) δ-phase. SEM images have shown the morphology of the stable samples. The conductivity and the operation temperature region of the samples have been determined from Arrhenius curves obtained from the FPPM measurements data and they vary from 1.83 to 9.95×10⁻¹ S cm⁻¹. Moreover, activation energy of the samples have been calculated by means of Arrhenius curves of the samples and relationships between them and the conductivity of the samples have been investigated in detail. The results obtained from XRD and FPPM measurements were confirmed by the DTA measurements.