Nanostructural Superconducting Metal-Oxide Materials
Tech Area / Field
- MAT-SYN/Materials Synthesis and Processing/Materials
- PHY-SSP/Solid State Physics/Physics
3 Approved without Funding
Institute of Microelectronics Technology and High Purity Materials, Russia, Moscow reg., Chernogolovka
- University of Tennessee, USA, TN, Knoxville\nUniversity of Houston / Texas Center for Superconductivity and Advanced Materials, USA, TX, Houston\nTechnische Universität Ilmenau / Zentrum fuer Micro- und Nanotechnologien, Germany, Ilmenau\nArizona State University, USA, AZ, Tempe\nUniversita degli Studi di Palermo / Dipartimento di Scienze Fisiche e Astronomiche, Italy, Palermo
Project summaryMetal-oxide superconductors are of much scientific and practical interest; they are the objects of numerous scientific and technological investigations. The practical interest is due to that copper-containing superconducting oxides are only materials known up to now, which are cooled by liquid nitrogen to achieve the superconducting state. The other materials need to be cooled by liquid helium or liquid hydrogen that is essentially more difficult from technical reasons and cost consuming. Unique strong-current (cables being capable to transmit electric power with low losses, solenoids generating super-strong magnetic fields, compact electric motors, levitation systems etc.) and weak-current (ultra-high frequency filters, sensitive electromagnetic field sensors, memory and logical computer cells etc.) devices of electrical engineering and electronics can be fabricated on the base of superconducting materials. The most perspective metal-oxide superconducting materials for practical applications both from their technical characteristics and cost are oxides of the Ln-Ba-Cu-O system, where Ln – a rare earth element (Y, Nd etc).
Scientific interest for studying metal-oxide superconductors is connected with revealing the superconductivity mechanism acting in these materials. The results of the latest studies of crystal structure and properties of oxide superconductors suggest the existence of structural and electronic inhomogeneity of oxide superconductors on nm-sized scale. The existence of inhomogeneity obliges reconsidering the widely spread notion about homogeneous phase composition and the known structures of superconducting oxides. It may be stated that the true crystalline structures of metal-oxide superconductors have not revealed so far that makes it impossible to describe elementary interactions in superconductor lattice resulting in electrons pairing properly. The presence of the inhomogeneity allows explaining a number of anomalous properties of superconducting oxides, and also determines physical characteristics thereof important for practical applications such critical current density and high-frequency surface impedance. The inhomogeneity problem must be regarded as the principal one both from an industrial standpoint and in respect to revealing the superconductivity mechanism.
The participants of this project have carried out detailed investigations of phase formation in perovskite metal-oxide systems, including superconducting ones. They concluded that the origin of inhomogeneous state of oxide superconductors results from their chemical inhomogeneity, which in its turn generates structural and electronic inhomogeneity. The chemical inhomogeneity arises due to the fact that simultaneous formation of proper superconducting and attendant non-superconducting phases takes place during synthesis of superconductors by universally used procedures. By virtue of very close crystallographic similarity, nm-sized crystallites of these phases are coherently intergrown, that produces illusion of homogenous material on a micro- and macroscopic scale. Structural studies of such inhomogeneous materials by long-range methods assigned them an averaged structure; physical properties thereof are determined by a combination of superconducting and non-superconducting constituents.
This project is aimed to solution chemical inhomogeneity of metal-oxide superconductors through technology development of single-phase formation of nanocrystals of superconducting phases. Fabrication of single-phase nanomaterial will allow to reveal true crystalline structures of metal-oxide superconductors and to describe inherent physical properties of superconducting phases without admixture of properties of non-superconducting ones.
One of the most important tendencies of modern electronics is an increasing of operation rate and information density, so it is currently central to create objects of decreasingly lower dimensions down to a few nanometers and to explore their properties. Creation and exploration of such objects give, on the one hand, a possibility to establish the fundamental lateral limitation for the existence of physical properties observed on microscopic size. On the other hand, it is probable to discover new physical effects only inherent to nm-sized objects and use them for elaborating the new types of electronic devices. It may be expected also that metal-oxide superconducting nanomaterials will be a new subject matter for studying and applications in electronics.
The main objects of the project:
- Detailed investigation of phase equilibria in the Y-Ba-Cu-O superconducting system and its parent Ba-Cu-O system with use of a complex of physical, chemical and structural methods.
- Development of fabrication technology of single-phase nanocrystals of Y-Ba-Cu-O superconductors and bulk superconducting nanomaterial.
- Studies of crystalline structures and physical properties of single superconducting nanocrystals and bulk superconducting nanomaterial.
A general working plan will include the following scientific tasks:
1. Synthesis of oxides of the Y-Ba-Cu-O and Ba-Cu-O systems in wide ranges of cationic composition, temperature and oxygen partial pressure. Analysis of phase transformations in the systems by a complex of physical-chemical and structural methods. Revealing discrete phases existing in the Y-Ba-Cu-O system, refinement of their cationic compositions.
2. Development of fabrication technology of YBaCuO nanocrystals. Investigation of Y-intercalation mechanism into BaCuO matrices oxides, synthesis of YBaCuO nanocrystals by intercalation procedure. Development of possibility to fabricate YBaCuO nanocrystals by low-temperature synthesis and zol-gel procedure. Establishing interlinks between phase and elemental composition of nanocrystals and synthesizing procedures. Fabrication of bulk superconducting nanomaterial.
3. Studies of crystalline structures by high-resolution methods. Investigation of physical characteristics of nanocrystals and bulk nanomaterials. Comparison of physical properties, integral and fine crystalline structure. Revealing correlation between physical characteristics and the degree of structural inhomogeneity.
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