Conduction properties of CaTi_1-xM_xO_3-α (M = Ga, Sc) at elevated temperatures

Conduction properties of CaTi_1-xM_xO_3-α (M = Ga, Sc) at high temperature were investigated using electrochemical methods. The ionic conductivity of CaTi_1-xSc_xO_3-α showed the highest value among those for CaTiO₃-based oxides ever reported and was comparable to that of 8YSZ in the range of 1073-1273 K. The conductivity of CaTi_1-xGa_xO_3-α was on the same level as that of CaTi_1-xAl_xO_3-α. The mobile ions in the specimens were mainly oxide ions. Hole conduction was included in the total conduction under the ordinary atmosphere and electronic conduction appeared in the region of low oxygen partial pressure. In addition, under intermediate range of oxygen partial pressure, the ionic conduction domain in which the conductivity was independent of oxygen partial pressure was also observed. Especially, Sc-doped specimens showed not only higher conductivity but also wider ionic domain and higher ion transference number than those for other CaTiO₃-based solid solutions under fuel cell condition.