Solid State Reaction of La(Co1−xNix)O3 with 10 mol%Y2O3–ZrO2

The reaction of cubic ZrO2, with La(Co1−xNix)O3 was investigated by hot pressing at 1573 K. The reaction can been seen for all of x. The compositions of the reacted areas were estimated as La2Zr2O7, La2Zr(Ni0.6Co0.4)O6 and La2ZrNiO6 for x=0, 0.4 and 1, respectively. The width of the reacted area decreased with increasing Ni fraction. The sintering of samples with compositions of the reacted areas mentioned above was made to investigate the crystal structures, electric resistivities and thermal expansion coefficients of the reacted compounds. The thermal expansion coefficients of the reacted compounds were always intermediate between those of cubic ZrO2 and La(Co1−xNix)O3. The electric resistivity of La2Zr2O7 was an extremely high order of 103 Ω·m even at the temperature of 1273 K. The substitution of Ni or Co for the Zr site decreases the electric resistivity and becomes the order of 10−1 Ω·m at the temperature of 1273 K. The electrode materials of cubic ZrO2 fuel cells are also discussed on the basis of the present experimental results.