An oxide superconductor includes: REBa.sub.2Cu.sub.3O.sub.7-x (RE being one element selected from a “RE element group” of Pr, Nd, Sm, Eu, Gd, Y, Tb, Dy, Ho, Er, Tm, Yb, and Lu). The RE includes at least three types of metallic elements (M1, M2, and M3), and the three types of metallic elements are any element of the RE element group selected in order. In an oxide system satisfying R(M1)≤20 mol % and R(M2)≥60 mol % and R(M3)≤20 mol %, R(M1) being an average metallic element ratio of M1 in M1+M2+M3, SD(Ms)>0.15 is satisfied at a position at 50% of an average film thickness of a cross section including the c-axis, Ms being the metallic element of not larger of R(M1) and R(M3), SD(Ms) being a standard deviation/average value of a concentration of Ms.

An oxide superconductor of an embodiment includes an oxide superconducting layer including at least one superconducting region containing barium (Ba), copper (Cu) and a first rare earth element, having a continuous perovskite structure, and having a size of 100 nm×100 nm×100 nm or more, and a non-superconducting region in contact with the at least one superconducting region, containing praseodymium (Pr), barium (Ba), copper (Cu),and a second. rare earth element, having a ratio of a number of atoms of the praseodymium (Pr) to a sum of a number of atoms of the second rare earth element and the number of atoms of the praseodymium (Pr) being 20% or more, having a continuous perovskite structure continuous with the continuous perovskite structure of the superconducting region, and having a size of 100 nm×100 nm×100 nm or more.

An oxide superconducting wire includes a superconducting layer deposited on a substrate. The superconducting layer includes an oxide superconductor RE-Ba—Cu—O and artificial pinning centers ABO.sub.3, where RE is a rare earth element, A is Ba, Sr or Ca, and B is Hf, Zr, or Sn. In a TEM image of a cross-section of the superconducting layer, a standard deviation σ of an inclination angle of the artificial pinning center rods with respect to a cross-sectional direction of the superconducting layer is 6.13° to 11.73° and an average length of the artificial pinning center rods is 19.84 to 25.44 nm.

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.

An oxide superconducting wire includes a superconducting layer deposited on a substrate. The superconducting layer includes an oxide superconductor RE-Ba—Cu—O and artificial pinning centers ABO.sub.3, where RE is a rare earth element, A is Ba, Sr or Ca, and B is Hf, Zr, or Sn. In a TEM image of a cross-section of the superconducting layer, a standard deviation σ of an inclination angle of the artificial pinning center rods with respect to a cross-sectional direction of the superconducting layer is 6.13° to 11.73° and an average length of the artificial pinning center rods is 19.84 to 25.44 nm.

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 μm and an average width of 1 to 2 μm, 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.

An oxygen sensor element made of a ceramic sintered body detects oxygen concentration based on an electric current value measured when a voltage is applied. The ceramic sintered body has a composition formula LnBa.sub.2-xSr.sub.xCu.sub.3O.sub.7- generated by substituting any element selected from group 2 elements in the periodic table, such as strontium (Sr), for a part of a composition formula LnBa.sub.2Cu.sub.3O.sub.7- (Ln denotes rare earth element and is 0 to 1). Sr substitution quantity x should satisfy an inequality constraint 0<x1.5. This allows provision of an oxygen sensor element that improves durability etc. without losing sensor characteristics.

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.

An oxide superconductor includes: REBa.sub.2Cu.sub.3O.sub.7-x (RE being one element selected from a RE element group of Pr, Nd, Sm, Eu, Gd, Y, Tb, Dy, Ho, Er, Tm, Yb, and Lu). The RE includes at least three types of metallic elements (M1, M2, and M3), and the three types of metallic elements are any element of the RE element group selected in order. In an oxide system satisfying R(M1)20 mol % and R(M2)60 mol % and R(M3)20 mol %, R(M1) being an average metallic element ratio of M1 in M1+M2+M3, SD(Ms)>0.15 is satisfied at a position at 50% of an average film thickness of a cross section including the c-axis, Ms being the metallic element of not larger of R(M1) and R(M3), SD(Ms) being a standard deviation/average value of a concentration of Ms.

Methods for producing oxide/metal composite components for use in high temperature systems, and components produced thereby. The methods use a fluid reactant and a porous preform that contains a solid oxide reactant. The fluid reactant contains yttrium as a displacing metal and the solid oxide reactant of the preform contains niobium oxide, of which niobium cations are displaceable species. The preform is infiltrated with the fluid reactant to react its yttrium with the niobium oxide of the solid oxide reactant and produce an yttria/niobium composite component, during which yttrium at least partially replaces the niobium cations of the solid oxide reactant to produce yttria and niobium metal, which together define a reaction product. The pore volume of the preform is at least partially filled by the reaction product, whose volume is greater than the volume lost by the solid oxide reactant as a result of reacting yttrium and niobium oxide.