Electrical properties of Sc-doped CaZrO3 solid electrolytes

The electrical conductivity of the solid electrolytes CaZr1–xScxO3–δ (x = 0.03 and 0.08) was investigated as a function of temperature in a humid air atmosphere. The total electrical conductivity was separated into bulk and grain boundary conductivity. The bulk conductivity for CaZr0.97Sc0.03O3–δ was found to be higher than that for CaZr0.92Sc0.08O3–δ. Using the oxygen partial pressure dependencies of electrical conductivity, the electron hole and ionic contributions to the total conductivity were distinguished. The oxides were found to be mixed ionic-electron hole conductors in air atmosphere and purely ionic conductors under reductive conditions. Transport numbers for ions and electron holes were calculated. At temperatures below 600 °C, the oxides are expected to behave as nearly pure ionic conductors under air conditions. Although the ionic conductivities for the oxides are comparable, the ionic transport numbers for CaZr0.97Sc0.03O3–δ were found to be higher than those for CaZr0.92Sc0.08O3–δ.