Multiple doping effect on the electrical conductivity in the (Ce(1-x-y)La(x)My)O2-delta (M = Ca, Sr) system

In order to clarify the co-doping effect on oxide-ion conductivity in the f luorite-type structure, electrical conductivity was measured for the solid- solution system, Ce1-x-yLaxMyO2-delta (M=Ca, Sr). The electrical conductivi ty in the Ce1-xLaxO2-x/2 system showed a maximum value at x = 0.15, and the n decreased gradually due to an ordering of oxygen vacancy. The decreased c onductivity at x = 0.34 increased again by partial substitution of M2+ in p lace 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.