Thesis (M.Sc.)--Chulalongkorn University, 2007

The structure, surface morphology, oxygen property and electrical conductivity of the Pr2Ni1-xMxO4, Pr2Ni1-xMxGa0.05O4 and Pr2Ni1-x-0.05MxGa0.05O4 (M = Cu, Co, In, Mg, Zn and x = 0.1-0.3) were investigated as a new mixed electronic and oxide ionic conductor for materials in Solid Oxide Fuel Cell (SOFC). The compounds were synthesized by modified citrate method and characterized by XRD and SEM. All perovskite showed K2NiF4–type with orthorhombic perovskite structure, homogeneous and dense microstructure, except Pr2Ni1-xMgxO4 (x=0.2, 0.3) and Pr2Ni1-xCoxGa0.05O4, Pr2Ni1-x-0.05CoxGa0.05O4 (x=0.2, 0.3). The effects of Ni-site dopant on oxygen property and electrical properties were studied. Oxygen property was determined by thermogravimetric analysis (TGA) and oxygen temperatureprogrammed desorption (O2-TPD). The result showed that the amounts of the oxygen permeation increased with the increasing amount of metal doped at Ni site, except Pr2Ni1-xInxO4. Ga–doped Pr2Ni1-xMxO4 stoichiometric compositions revealed the highest value of oxygen permeation. The conductivity was improved by doping Cu and Zn. Especially, doping 15% Cu is the most effective for enhancing the electrical conductivity of Pr2NiO4. The Pr2Ni0.85Cu0.15O4 ceramic exhibited an electrical conductivity of 123.7 S-1cm-1 at 550°C, which was about 50% higher than that of Pr2NiO4 (82.5 S-1cm-1 at 550°C). However, Ga–doped at the B site ions decreased the electrical conductivity.