A solid oxide fuel cell comprises a solid electrolyte layer, a barrier layer, and a cathode. The cathode includes a cathode current collecting layer and a cathode active layer. The cathode active layer includes a plurality of micro-cracks in a surface region within a predetermined distance from the interface between the barrier layer and the cathode active layer.

A solid oxide fuel cell comprises a solid electrolyte layer, a barrier layer, and a cathode. The cathode includes a cathode current collecting layer and a cathode active layer. The cathode active layer includes a plurality of micro-cracks in an interface region within a predetermined distance from the interface between the cathode current collecting layer and the cathode active layer.

A method of producing polycrystalline Y.sub.3Ba.sub.5Cu.sub.8O.sub.y (Y-358) whereby powders of yttrium (III) oxide, a barium (II) salt, and copper (II) oxide are pelletized, calcined at 850 to 950 C. for 8 to 16 hours, ball milled under controlled conditions, pelletized again and sintered in an oxygen atmosphere at 900 to 1000 C. for up to 72 hours. The polycrystalline Y.sub.3Ba.sub.5Cu.sub.8O.sub.y thus produced is in the form of elongated crystals having an average length of 2 to 10 m and an average width of 1 to 2 m, and embedded with spherical nanoparticles of yttrium deficient Y.sub.3Ba.sub.5Cu.sub.8O.sub.y having an average diameter of 5 to 20 nm. The spherical nanoparticles are present as agglomerates having flower-like morphology with an average particles size of 30 to 60 nm. The ball milled polycrystalline Y.sub.3Ba.sub.5Cu.sub.8O.sub.y prepared under controlled conditions shows significant enhancement of superconducting and flux pinning properties.

A superconducting composition of matter including overlapping first and second regions. The regions comprise unit cells of a solid, the first region comprises an electrical insulator or semiconductor, and the second region comprises a metallic electrical conductor. The second region extends through the solid and a subset of said second region comprise surface metal unit cells that are adjacent to at least one unit cell from the first region. The ratio of the number of said surface metal unit cells to the total number of unit cells in the second region being at least 20 percent.

A superconducting composition of matter including overlapping first and second regions. The regions comprise unit cells of a solid, the first region comprises an electrical insulator or semiconductor, and the second region comprises a metallic electrical conductor. The second region extends through the solid and a subset of said second region comprise surface metal unit cells that are adjacent to at least one unit cell from the first region. The ratio of the number of said surface metal unit cells to the total number of unit cells in the second region being at least 20 percent.

Provided are: a sintered oxide which is capable of obtaining low carrier density and high carrier mobility when configured as an oxide semiconductor thin film by using a sputtering method; and a sputtering target which uses the same. The sintered oxide contains indium, gallium and copper as oxides. It is preferable for the gallium content to be at least 0.08 and less than 0.20 when expressed as an atomic ratio (Ga/(In+Ga)), the copper content to be at least 0.001 and less than 0.03 when expressed as an atomic ratio (Cu/(In+Ga+Cu)), and for the sintering to be performed at 1,200-1,550 C., inclusive. A crystalline oxide semiconductor thin film obtained by forming this sintered oxide as a sputtering target makes it possible to achieve a carrier density of 1.010.sup.18 cm.sup.3 or lower, and a carrier mobility of 10 cm.sup.2 V.sup.1 sec.sup.1 or higher.

Provided are: a sintered oxide which is capable of obtaining low carrier density and high carrier mobility when configured as an oxide semiconductor thin film by using a sputtering method; and a sputtering target which uses the same. The sintered oxide contains indium, gallium and copper as oxides. It is preferable for the gallium content to be at least 0.08 and less than 0.20 when expressed as an atomic ratio (Ga/(In+Ga)), the copper content to be at least 0.001 and less than 0.03 when expressed as an atomic ratio (Cu/(In+Ga+Cu)), and for the sintering to be performed at 1,200-1,550 C., inclusive. A crystalline oxide semiconductor thin film obtained by forming this sintered oxide as a sputtering target makes it possible to achieve a carrier density of 1.010.sup.18 cm.sup.3 or lower, and a carrier mobility of 10 cm.sup.2 V.sup.1 sec.sup.1 or higher.

Provided are: a sintered oxide which is capable of obtaining low carrier density and high carrier mobility when configured as an oxide semiconductor thin film by using a sputtering method; and a sputtering target which uses the same. The sintered oxide contains indium, gallium and copper as oxides. It is preferable for the gallium content to be 0.20-0.45, inclusive, when expressed as an atomic ratio (Ga/(In+Ga)), the copper content to be at least 0.001 and less than 0.03 when expressed as an atomic ratio (Cu/(In+Ga+Cu)), and for the sintering to be performed at 1,200-1,550 C., inclusive. A crystalline oxide semiconductor thin film obtained by forming this sintered oxide as a sputtering target makes it possible to achieve a carrier density of 3.010.sup.18 cm.sup.3 or lower, and a carrier mobility of 10 cm.sup.2V.sup.1 sec.sup.1 or higher.

Provided are: a sintered oxide which is capable of obtaining low carrier density and high carrier mobility when configured as an oxide semiconductor thin film by using a sputtering method; and a sputtering target which uses the same. The sintered oxide contains indium, gallium and copper as oxides. It is preferable for the gallium content to be 0.20-0.45, inclusive, when expressed as an atomic ratio (Ga/(In+Ga)), the copper content to be at least 0.001 and less than 0.03 when expressed as an atomic ratio (Cu/(In+Ga+Cu)), and for the sintering to be performed at 1,200-1,550 C., inclusive. A crystalline oxide semiconductor thin film obtained by forming this sintered oxide as a sputtering target makes it possible to achieve a carrier density of 3.010.sup.18 cm.sup.3 or lower, and a carrier mobility of 10 cm.sup.2V.sup.1 sec.sup.1 or higher.

There are provided an oxide dielectric having excellent properties and a solid state electronic device (e.g., a capacitor, a semiconductor device, or a small electromechanical system) having such an oxide dielectric.

An oxide layer 30 includes an oxide dielectric (possibly including inevitable impurities) including bismuth (Bi) and niobium (Nb) and having a first crystal phase of a pyrochlore-type crystal structure and a second crystal phase of a -BiNbO.sub.4-type crystal structure. The oxide layer 30 has a controlled content of the first crystal phase and a controlled content of the second crystal phase, in which the first crystal phase has a dielectric constant that decreases with increasing temperature of the oxide layer 30 in a temperature range of 25 C. or more and 120 C. or less, and the second crystal phase has a dielectric constant that increases with increasing temperature of the oxide layer 30 in the temperature range.