Conductivity measurement of scandium doped barium zirconate for fuel cell application

A pseudoternary phase diagram of the BaO-ZrO₂-ScO_1.5 system is established and the conductivities of the scandium-doped barium zirconate are measured in wet conditions. According to the phase diagram, the molar fraction of scandia in the barium zirconate phase that equilibrates with the cubic zirconia (ZrO₂) and scandia (Sc₂O₃) phase is 0.03. On the composition line, where the molar fraction of barium oxide (BaO) is 0.50, the solubility of scandia into barium zirconate is 0.27 as a molar fraction of scandia. At around 500°C, the conductivities of scandium-doped barium zirconate are estimated to be almost same as that of yttrium-doped barium zirconate. The activation energies for bulk proton conduction in scandium-doped barium zirconate (0.57 eV for BaZr _0.90Sc_0.10O_3-δ) are higher than that of yttrium-doped barium zirconate (0.44 eV for BaZr_0.90Y _0.10O_3-δ). In addition, the bulk conductivity of scandium-doped barium zirconate in this study is 10 times higher than the reported conductivities in the temperature range of 75°C to 300°C.