2000 Volume 68 Issue 6 Pages 455-459
In order to clarify the co-doping effect on oxide-ion conductivity in the fluorite-type structure, electrical conductivity was measured for the solid-solution system, Ce1-x-yLaxMyO2-δ (M = Ca, Sr). The electrical conductivity in the Ce1-xLaxO2-x/2 system showed a maximum value at x = 0.15, and then decreased gradually due to an ordering of oxygen vacancy. The decreased conductivity at x = 0.34 increased again by partial substitution of M2+ in place of La3+. This phenomenon was named as ``multiple doping effect’’, which was understood to suppress the ordering of oxygen vacancy on a basis of the estimation of the configurational entropy.