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Lanthanum chromites doped with alkaline earth metals are candidate materials for SOFC interconnectors. The oxide ionic conductivity of the material is important in estimating the oxygen permeability through the interconnector. The oxide ionic conductivity ( σ i ) of lanthanum chromites was measured using the electron quasi-blocking method under various oxygen partial pressures. Dense lanthanum chromite films deposited on crystal yttria stabilized zirconia (YSZ) plates by laser ablation were used as specimens. Under high oxygen partial pressure ( P O 2 = 1 −10 −3 atm ), σ i ; increased proportional to the 1 2 power of P O 2 , while under low oxygen partial pressure ( P O 2 −4 atm) σ i increased as P O 2 decreased. These results indicate that the ionic conduction of lanthanum chromites is controlled by more than two mechanisms. Since the dependence of σ i on P O 2 under the low oxygen pressure is consistent with that of the oxygen vacancy concentration of lanthanum chromites, the ionic conduction at this range of P O 2 is interpreted to be controlled by the oxygen vacancy diffusion.

A-site deficient La(Sr)CrO 3 − δ thin film interconnectors were successfully fabricated on porous La(Sr)MnO x tubes using high deposition rate laser ablation. The La(Sr)CrO 3 − δ films obtained by this method are dense and void-free. The film deposition rate was about 10 μm/min. The substrate could easily be masked in order to deposit the films in the desired shape. The substrate tube was heated at 873–1073 K. As the substrate temperature was much lower than the sintering temperature of the substrate tube, the porous micro-structures of the substrate tube were maintained. The difference in chemical composition between the film and the target was negligible.

La−xSrxCrO3−δ films were fabricated on yttria stabilized zirconia (YSZ) and La(Sr)MnO3 polycrystal substrates using the laser ablation method. At a substrate temperature of 973 K and an oxygen pressure of 10−4 Torr, the resultant films were porefree and contained no detectable oxygen vacancy. The chemical composition of the films almost agreed with the target. Film crystallinity depended on the crystal structure of the substrates. The film formed on YSZ substrate showed remarkable primary particle growth resulting from heat-treatment at 1473 K for 5 h in air. When a film was formed on the LaMnO3 substrate, which has a crystal structure similar to that of LaCrO3, under the same conditions as above, neither crystal structure change nor particle growth was observed from heat-treatment at 1473 K.

Tubular-type solid oxide fuel cell (SOFC) with interconnector has been successfully fabricated, with a maximum single cell power density of 0.9 W/cm2, the highest value reported so far. A self supporting La(Sr)MnOx tube was used for the cathode. The La(Sr)CrOx interconnector was made using the laser oblation method. The yttria-stabilized zirconia (YSZ) electrolyte and Ru/YSZ cermet anode were fabricated by the electrochemical vapor deposition (EVD) process.

Ru/YSZ cermet SOFC anodes were fabricated using the EVD method. Ru has high sintering resistivity compared with Ni. During the power generation tests at 1273 K the Ru/YSZ cermet anode showed high activity for hydrogen oxidation compared with conventional Ni/YSZ cermet anodes. Especially in the high current density of a maximum of 3200 mA/cm2 the ac polarization value was reduced to approximately 200 mV. Tubular type SOFCs were made by depositing 10 micro m thick 10 mol% yttriastabilized zirconia (YSZ) electrolyte films on porous La(Sr)MnOx cathode tubes using the EVD process and then making a Ru/YSZ cermet anode on YSZ. The cells had the highest power generation density with a maximum density of 1550 mW/cm2. After the power generation test of approximately one week including several thermal cycles, the anode polarization was unchanged and there was no change in the Ru metal grain size.