A process for the growth of new, and difficult-to-synthesize, metal oxide, and other mixed anion oxide-based, single crystals from a molten metal flux. Metal fluxes are new for the growth of metal oxide single crystals. Preliminary reactions proved that new phases and phases that normally require costly, extreme conditions do grow as single crystals. Batches of individual reactions are heat-treated to synthesize single crystals comprised of oxygen with one or more transition, alkaline-earth and/or lanthanide metals, and can also include other anions like chalcogens or pnictogens, or halides. The reactivity and the propensity for crystallization of charge compensated single crystals from alkaline earth fluxes have been made evident by the results presented here.

A substrate structure is provided for use in a superconductive device. The substrate structure has at least one of its two opposite surfaces configured for carrying at least one superconductive structure thereon. The substrate structure comprises a substrate made of a dielectric material composition and having a tape-like shape of a predetermined geometry characterized by a width-thickness aspect ratio of at least 10 and global planarity of said at least one surface defined by a surface roughness on a nanometric scale substantially not exceeding 1 nm rms.

A method of forming a high-temperature superconducting single crystal is capable of facilitating a high-temperature superconducting single crystal containing rare-earth metals to grow using a multilayer seed. The method includes: preparing a rare earth barium copper oxide (ReBCO)-based precursor containing rare-earth metals; preparing a plurality of seeds that differ in lattice constant; placing the prepared seeds on top of the precursor through stacking; melting a portion of the precursor by heating the precursor to a peritectic temperature thereof or higher; and growing a single crystal by cooling the precursor to a crystal growth temperature thereof to match a crystal orientation of the seeds. Despite being used to increase the area and maintain the soundness of the single-crystalline specimen in most single-crystal growth, a buffer herein is to facilitate a single crystal of a new composition to grow.

A method for recycling rare-earth barium copper oxide (REBCO) bulk seed crystals to grow a superconducting bulk is provided, in which a first precursor and a first buffer layer are prepared, and based on a top-seeded melt-texture growth method, an original REBCO superconducting bulk is obtained, which is cleaved to obtain a recycled seed crystal; the recycled seed crystal is subjected to grinding and polishing; a second precursor and a second buffer layer are prepared, and the recycled seed crystal is inserted between the second precursor and the second buffer layer; the precursor assembly is treated through the top-seeded melt-texture growth method to obtain a REBCO superconducting bulk grown from the recycled seed crystal.

A method for preparing a high-performance REBCO high-temperature bulk superconductor based on a layered precursor pellet includes: obtaining original reagents with preset molar ratios, and preparing original powders by a solid-phase sintering method; preparing three types of precursor powder combinations by mixing the original powders with preset molar ratios; pressing and stacking the precursor powder combinations to obtain a combined precursor pellet, pressing buffer precursor powders to obtain a buffer layer; processing an REBCO original seed crystal, the combined precursor pellet and the buffer layer based on a preset top-seeded melt texture growth method to obtain an initial REBCO high-temperature bulk superconductor; and performing annealing treatment according to the initial REBCO high-temperature bulk superconductor to obtain a final REBCO high-temperature bulk superconductor. The method achieves the refinement of the second phase particles in the solid solution by the modified precursor powders, and improves the superconducting performance of the bulk material.

New polycrystalline materials having yttrium aluminum perovskite (YAP) and yttrium zirconate (YZ) are described. In one aspect, a polycrystalline material (e.g., a bulk or monolithic polycrystalline material) may comprise (a) at least 50 wt. % yttrium aluminum perovskite (YAP) phase, and (b) at least 0.1 wt. % yttrium zirconate (YZ) phase. Such polycrystalline materials may realize an improved combination of properties, such as an improved combination of two or more of density, modulus of rupture (MOR), fracture toughness, dielectric strength, loss tangent, and plasma etch resistance, among others.