Preparation of La₂-xCaxNi₁-yCoy(Ga, Ti)zO₄ for solid oxide fuel cell

Abstract

The properties of La₂-xCaxNi₁-yCoy(Ga, Ti)zO₄+d (x = 0.0-1.0, y = 0.1-0.2, z = 0.00-0.1, 0.2) cathode materials for solid oxide fuel cell were studied. It was found that the K₂NiF₄-type perovskite structure synthesized by the modified citrate method was obtained from La₂Ni₁-yCoyO₄+d (y = 0.1-0.2) calcined and sintered at 1200ºC and 1300ºC, respectively, for 6 hrs. The highest oxygen permeation rate was obtained from the La₂Ni₀.₉Co₀.₁O₄+d for 0.78 µmol/s.cm² at 1000ºC. The electrical conductivity of La₂Ni₀.₉Co₀.₁O₄+d increased with the doping of Ca²+ ion in La³⁺ site for La₂-xCaxNi₀.₉Co₀.₁O₄+d (x = 0.0-1.0). However, the single phase of K₂NiF4-type structure was only achieved when x = 0.5. The electrical conductivity of the La₁.₅Ca₀.₅Ni₀.₉Co₀.₁O₄+d reached the maximum value of 106.3 S/cm at 800ºC and the oxygen permeation rate was 0.48 µmol/s.cm² at 1000ºC. The addition of Ga³⁺and Ti₄+ ions on La1.5Ca0.5Ni0.9Co0.1(Ga, Ti)zO₄+d (z = 0.00-0.1, 0.2) was investigated. For Ga³⁺ ion addition, all of compositions showed the single phase of K₂NiF4-type structure. The highest oxygen permeation rate was obtained for 0.49 µmol/s.cm² at 1000ºC on Ga³⁺ ion doping of z = 0.01, while the electrical conductivity was decreased to 60.12 S/cm at 800ºC. Additionally, the addition of Ti4+ ion with z = 0.01-0.05 showed the single phase of K₂NiF4-type structure. The oxygen permeation rate and the electrical conductivity were tentatively decreased with an increase of Ti4+ ion.