Hydrothermal preparation and electrochemical properties of Gd~(3+) and Bi~(3+), Sm~(3+), La~(3+), and Nd~(3+) codoped ceria-based electrolytes for intermediate temperature-solid oxide fuel cell

摘要

The structure, the thermal expansion coefficient, electrical conductivities of Ce_(0.8)Gd_(0.2-x)M_xO_(2-δ) (for M: Bi, x = 0-0.1, and for M: Sm, La, and Nd, x = 0.02) solid solutions, prepared for the first time hydrothermally, are investigated. The uniformly small particle size (28-59 nm) of the materials allows sintering of the samples into highly dense ceramic pellets at 1300-1400 ℃. The maximum conductivity, σ_(700℃) around 4.46 × 10~(-2)S cm~(-1) with E_δ = 0.52eV, is found at x = 0.1 for Bi-co-doping. Among various metal-co-dopings, for x = 0.02, the maximum conductivity, σ_(700℃) around 2.88 × 10~(-2) S cm~(-1) with E_a = 0.67 eV, is found for Sm-co-doping. The electrolytic domain boundary (EDB) of Ce_(0.8)Gd_(0.1)Bi_(0.1)O_(2-δ) is found to be 1.2 × 10~(-19) atm, which is relatively lower than that of the singly doped samples. The thermal expansion coefficients, determined from high-temperature X-ray data are 11.6 × 10~(-6)K~(-1) for the CeO_2, 12.1 × 10~(-6) K~(-1) for Ce_(0.8)Gd_(0.2)O_(2-δ), and increase with co-doping to 14.2 × 10~(-6) K~(-1) for Ce_(0.8)Gd_(0.18)Bi_(0.02)O_(2-δ). The maximum power densities for the single cell based on the codoped samples are higher than that of the singly doped sample. These results suggest that co-doping can further improve the electrical performance of ceria-based electrolytes.