According to the present invention, a piezoelectric film having a single crystal structure is able to be formed, from various piezoelectric materials, on a film structure of the present invention. A film structure according to the present invention includes: a substrate; a buffer film which is formed on the substrate and has a tetragonal crystal structure containing zirconia; a metal film containing a platinum group element, which is formed on the buffer film by means of epitaxial growth; and a film containing Sr(Ti.sub.1−x, Ru.sub.x)O.sub.3 (wherein 0≤x≤1), which is formed on the metal film by means of epitaxial growth.

A superconductor wire can achieve a J.sub.e of at least 600 A/mm.sup.2 at 4.2 K, 20 T applied magnetic field, which is greater than J.sub.e previously reported in the literature. The superconductor wire can include superconductor tape stands that have I.sub.c per total strand width of at least 125 A/mm at 4.2 K, 20 T applied magnetic field. In an embodiment, the superconductor wire can have superconductor film with a modified REBCO composition, where (Ba+M)/Cu is at least 0.72. In the same or different embodiment, the superconductor film can have a thickness of at least 3 microns. The superconductor tape strands can have a stabilizer layer, where the thickness of the stabilizer is selected so that the neutral plane of the strands is near or passes through the superconductor film. A superconductor cable can be made from superconductor wires.

An oxide superconductor of an embodiment includes an oxide superconductor layer having a continuous Perovskite structure containing rare earth elements, barium (Ba), and copper (Cu). The rare earth elements contain a first element which is praseodymium (Pr), at least one second element selected from the group consisting of neodymium (Nd), samarium (Sm), europium (Eu), and gadolinium (Gd), at least one third element selected from the group consisting of yttrium (Y), terbium (Tb), dysprosium (Dy), and holmium (Ho), and at least one fourth element selected from the group consisting of erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

An oxide superconducting wire includes a superconducting laminate including an oxide superconducting layer disposed, either directly or indirectly, on a substrate, and a stabilization layer which is a Cu plating layer covering an outer periphery of the superconducting laminate, and a Vickers hardness of the Cu plating layer is in the range of 80 to 190 HV.

Methods and devices for producing a superconductive conductor are disclosed. The method includes providing a plurality of conductive strips by means of a strip provision device, applying liquid soldering agent onto the plurality of conductive strips, stacking the conductive strips wetted with soldering agent, and forming a superconductive body by machining the strip stack.

An oxide superconductor of an embodiment includes an oxide superconductor layer having a continuous Perovskite structure including rare earth elements, barium (Ba), and copper (Cu). The rare earth elements include a first element which is praseodymium, at least one second element selected from the group consisting of neodymium, samarium, europium, and gadolinium, at least one third element selected from the group consisting of yttrium, terbium, dysprosium, and holmium, and at least one fourth element selected from the group consisting of erbium, thulium, ytterbium, and lutetium. When the number of atoms of the first element is N(PA), the number of atoms of the second element is N(SA), and the number of atoms of the fourth element is N(CA), 1.5×(N(PA)+N(SA))≤N(CA) or 2×(N(CA)−N(PA))≤N(SA) is satisfied.

A process for producing a process for producing a LnM.sub.2Cu.sub.3O.sub.x high-temperature superconductive powder, the process comprising: i) providing an aqueous solution of Ln, M and Cu and at least one mineral acid; ii) adding at least one sequestrating agent and, optionally, at least one dispersant to the solution to form a precipitate; iii) recovering the precipitate from the solution; and iv) heating the precipitate in a flow of oxygen to form the LnM.sub.2Cu.sub.3O.sub.x powder, wherein Ln is a rare earth element, preferably Y, Ce, Dy, Er, Gd, La, Nd, Pr, Sm, Sc, Yb, or a mixture of two or more thereof, and wherein M is selected from Ca, Sr, and Ba.

An ultra-thin film superconducting tape and method for fabricating same is disclosed. Embodiments are directed to a superconducting tape being fabricated by processes which include removing a portion of the superconducting tape's substrate subsequent the substrate's initial formation, whereby a thickness of the superconducting tape is reduced to 15-80 μm.

A superconducting material includes YBa.sub.2Cu.sub.3O.sub.7-δ and a nano-structured, preferably nanowires, WO.sub.3 dopant in a range of from 0.01 to 3.0 wt. %, preferably 0.075 to 0.2 wt. %, based on total material weight. Methods of making the superconductor may preferably avoid solvents and pursue solid-state synthesis employing Y, Ba, and/or Cu oxides and/or carbonates.

An oxide superconducting thin film material includes: a metal substrate having a surface with a biaxially oriented crystal orientation structure; an intermediate layer biaxially oriented and formed on the metal substrate; and an oxide superconducting thin film formed on the intermediate layer and composed of a RE123-based oxide superconductor represented by REBa.sub.2Cu.sub.3O.sub.y. The oxide superconducting thin film includes Br (bromine).