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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.

In order to clarify the reaction mechanism on SOFC cathode, it is necessary to evaluate the contribution of oxygen bulk diffusion of electrode materials. In this work, the authors prepared dense Sr-doped lanthanum manganites (LSM) films on yttria stabilized zirconia (YSZ) substrates by a laser ablation method using KrF eximer laser. Scanning electron microscopy measurements indicated that dense LSM films (6--32{micro}m) were formed. Using these samples, electrochemical properties (oxide-ionic conductivity and ac impedance) were measured in Ar-O{sub 2} atmospheres.

The electrochemical properties of La(M)MnO{sub x}(M = Sr,Ca)/YSZ fabricated by CVD-EVD method were studied. It is indicated by the experimental results using O{sub 2}/N{sub 2} and O{sub 2}/He as the cathode gas that the gas diffusion process at micro pores around the La(M)MnO{sub x}/YSZ interface mainly determines the rate of cathode reaction. The cathode had an extremely large phase boundary and the polarization was about 1mV at a current density of 1.5A/cm{sup 2} in the oxygen at 1,273K. It showed almost the same value at 1,073K. The film growth of Ru/YSZ anode fabricated with the EVD process was examined. The structures of Ru/YSZ cermet were controlled by the thickness of YSZ electrolyte film and the reaction temperature.

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.

La(Sr)MnO[sub 3] cathodes have been investigated as high temperature oxygen reduction electrodes in the solid oxide fuel cells (SOFCs). The cathodes consist of 10 mole percent of yttria stabilized zirconia (YSZ) thin film electrolyte layer deposited on a porous La[sub 0.81]Sr[sub 0.09]MnO[sub 3] tube using the electrochemical vapor deposition method. The La(Sr)MnO[sub 3]/YSZ cathodes have different electrochemical properties from those fabricated with the sintering method. The cathode polarization was about 1 mV at a current density of 1.5 A/cm[sup 2] in oxygen at 1,000 C. This type of cathode has an extremely large phase boundary and large interfacial capacitance (more than 1 F/cm[sup 2]) which is approximately proportional to the oxygen partial pressure.

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.

This paper reports that, the authors succeeded in fabricating a solid-oxide-electrolyte fuel cell, with the highest power-generation density, with a maximum single-cell-level density of 1550 mW/cm{sup 2}. This cell was made by depositing a 10{mu}m thick 10 mol% (m/o) yttria stabilized zirconia (YSZ) electrolyte layer on a porous La(Sr)MnO{sub x} cathode tube using the electrochemical vapor deposition method and then making a Ru/YSZ cermet anode on top of it.

La(Sr)MnO[sub 3] cathodes have been investigated as high temperature oxygen reduction electrodes in the solid oxide fuel cells (SOFCs). The cathodes consist of 10 mole percent of yttria stabilized zirconia (YSZ) thin film electrolyte layer deposited on a porous La[sub 0.81]Sr[sub 0.09]MnO[sub 3] tube using the electrochemical vapor deposition method. The La(Sr)MnO[sub 3]/YSZ cathodes have different electrochemical properties from those fabricated with the sintering method. The cathode polarization was about 1 mV at a current density of 1.5 A/cm[sup 2] in oxygen at 1,000 C. This type of cathode has an extremely large phase boundary and large interfacial capacitance (more than 1 F/cm[sup 2]) which is approximately proportional to the oxygen partial pressure.

This paper reports that, the authors succeeded in fabricating a solid-oxide-electrolyte fuel cell, with the highest power-generation density, with a maximum single-cell-level density of 1550 mW/cm{sup 2}. This cell was made by depositing a 10{mu}m thick 10 mol% (m/o) yttria stabilized zirconia (YSZ) electrolyte layer on a porous La(Sr)MnO{sub x} cathode tube using the electrochemical vapor deposition method and then making a Ru/YSZ cermet anode on top of it.