Methods for forming a metal oxide electrolyte improve ionic conductivity. Some of those methods involve applying a first metal compound to a substrate, converting that metal compound to a metal oxide, applying a different metal compound to the metal oxide, and converting the different metal compound to form a second metal oxide. That substrate may be in nanobar form that conforms to an orientation imparted by a magnetic field or an electric field applied before or during the converting. Electrolytes so formed can be used in solid oxide fuel cells, electrolyzers, and sensors, among other applications.

Methods for forming a metal oxide electrolyte improve ionic conductivity. Some of those methods involve applying a first metal compound to a substrate, converting that metal compound to a metal oxide, applying a different metal compound to the metal oxide, and converting the different metal compound to form a second metal oxide. That substrate may be in nanobar form that conforms to an orientation imparted by a magnetic field or an electric field applied before or during the converting. Electrolytes so formed can be used in solid oxide fuel cells, electrolyzers, and sensors, among other applications.

In an electrolyte sheet for a solid oxide fuel cell according to the present invention, the number of flaws on at least one of surfaces of the sheet detected by a fluorescent penetrant inspection is 30 points or less in each of sections obtained by dividing the sheet into the sections each measuring 30 mm or less on a side. A unit cell for a solid oxide fuel cell according to the present invention comprises a fuel electrode, an air electrode, and the electrolyte sheet for a solid oxide fuel cell according to the present invention, which is disposed between the fuel electrode and the air electrode. A solid oxide fuel cell of the present invention includes the unit cell for a solid oxide fuel cell according to the present invention.

In an electrolyte sheet for a solid oxide fuel cell according to the present invention, the number of flaws on at least one of surfaces of the sheet detected by a fluorescent penetrant inspection is 30 points or less in each of sections obtained by dividing the sheet into the sections each measuring 30 mm or less on a side. A unit cell for a solid oxide fuel cell according to the present invention comprises a fuel electrode, an air electrode, and the electrolyte sheet for a solid oxide fuel cell according to the present invention, which is disposed between the fuel electrode and the air electrode. A solid oxide fuel cell of the present invention includes the unit cell for a solid oxide fuel cell according to the present invention.

An object of the present invention is to provide a hydrogen permeable material having excellent hydrogen permeability. Another object of the present invention is to provide a composite member and a fuel cell including the hydrogen permeable material. The hydrogen permeable material comprises a perovskite type compound represented by the following general formula (1a). In another embodiment, the hydrogen permeable material comprises a hydrogen-containing perovskite type compound, which is the perovskite type compound represented by the general formula (1a) with introduced hydride ion (H.sup.−). Wherein M is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca, x is a numerical value of 0 or more and 0.3 or less, y is a numerical value of more than 0 and 0.75 or less, w is a value at which an average valence of In is +1.0 or more and +2.5 or less, and y≥w.

M.sub.1-xZr.sub.1-yIn.sub.yO.sub.3-x-0.5y-2  (1a)

An object of the present invention is to provide a hydrogen permeable material having excellent hydrogen permeability. Another object of the present invention is to provide a composite member and a fuel cell including the hydrogen permeable material. The hydrogen permeable material comprises a perovskite type compound represented by the following general formula (1a). In another embodiment, the hydrogen permeable material comprises a hydrogen-containing perovskite type compound, which is the perovskite type compound represented by the general formula (1a) with introduced hydride ion (H.sup.−). Wherein M is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca, x is a numerical value of 0 or more and 0.3 or less, y is a numerical value of more than 0 and 0.75 or less, w is a value at which an average valence of In is +1.0 or more and +2.5 or less, and y≥w.

M.sub.1-xZr.sub.1-yIn.sub.yO.sub.3-x-0.5y-2  (1a)

A fuel cell comprises an anode, a cathode, and a solid electrolyte layer disposed between the anode and the cathode. The cathode includes a main phase configured by a perovskite oxide including at least one of La or Sr at the A site and that is expressed by the general formula ABO.sub.3, and a secondary phase configured by strontium oxide. The occupied surface area ratio of the secondary phase in a cross section of the cathode is greater than or equal to 0.05% and less than or equal to 3%.

A fuel cell comprises an anode, a cathode, and a solid electrolyte layer disposed between the anode and the cathode. The cathode includes a main phase configured by a perovskite oxide including at least one of La or Sr at the A site and that is expressed by the general formula ABO.sub.3, and a secondary phase configured by strontium oxide. The occupied surface area ratio of the secondary phase in a cross section of the cathode is greater than or equal to 0.05% and less than or equal to 3%.

Described are energy storage devices employing a gas storage structure, which can accommodate or store gas evolved from the energy storage device. The energy storage device comprises an electrochemical cell with electrodes comprising metal-containing compositions, like metal oxides, metal nitrides, or metal hydrides, and a solid state electrolyte.

Described are energy storage devices employing a gas storage structure, which can accommodate or store gas evolved from the energy storage device. The energy storage device comprises an electrochemical cell with electrodes comprising metal-containing compositions, like metal oxides, metal nitrides, or metal hydrides, and a solid state electrolyte.