Tb_xCe_(0.95-x)Gd_(0.05)O_(2-δ) (0.15 ≤ x ≤ 0.40) Cathode Materials Prepared Through Solid State Route for Low Temperature SOFC

摘要

Four compositions of Tb_xCe_(0.95-x)Gd_(0.05)O_(2-δ) (0.15 ≤ x ≤ 0.40) have been prepared by varying the Tb content. Phase formation, thermal expansion, ionic conductivity, electronic conductivity, ionic transference number and optical properties have been investigated. XRD results indicate that Tb_xCe_(0.95-x)Gd_(0.05)O_(2-δ) (TCGO) samples crystallize in the fluorite structure. The coefficient of thermal expansion decreases with increasing x, and at x= 0.2 shows comparable TEC value of (12.8 × 10~(-6) K~(-1)) with that of Ce_(0.80)Gd_(0.20)O_2 (GDC) electrolyte at 50-800 °C temperature range. A maximum electrical conductivity of 0.008 S cm"' is exhibited by the composition, x = 0.40 at 550 °C. Gd~(3+) contributes to ionic conduction by creating oxygen vacancies and Tb~(4+) contributes to electronic conduction by decreasing the band gap of CeO_2. UV-Visible spectroscopy results show a band gap of 3.19 eV for pure GDC and 1.85 eV for the composition Tb_(0.20)Ce_(0.75)Gd_(0.05)O_(2-δ).