HOME

TheInfoList



OR:

Yttrium barium copper oxide (YBCO) is a family of
crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...
line
chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
s that display
high-temperature superconductivity High-temperature superconductors (abbreviated high-c or HTS) are defined as materials that behave as superconductors at temperatures above , the boiling point of liquid nitrogen. The adjective "high temperature" is only in respect to previou ...
; it includes the first material ever discovered to become
superconducting Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlike ...
above the boiling point of liquid nitrogen (77 K) at about 93 K. Many YBCO compounds have the general formula Y Ba2 Cu3 O7−''x'' (also known as Y123), although materials with other Y:Ba:Cu ratios exist, such as Y Ba2 Cu4 Oy (Y124) or Y2 Ba4 Cu7 Oy (Y247). At present, there is no singularly recognised theory for high-temperature superconductivity. It is part of the more general group of rare-earth barium copper oxides (ReBCO) in which, instead of yttrium, other rare earths are present.


History

In April 1986,
Georg Bednorz Johannes Georg Bednorz (; born 16 May 1950) is a German physicist who, together with K. Alex Müller, discovered high-temperature superconductivity in ceramics, for which they shared the 1987 Nobel Prize in Physics. Life and work Bednorz was bor ...
and Karl Müller, working at IBM in Zurich, discovered that certain semiconducting oxides became superconducting at relatively high temperature, in particular, a lanthanum barium copper oxide becomes superconducting at 35 K. This oxide was an oxygen-deficient
perovskite Perovskite (pronunciation: ) is a calcium titanium oxide mineral composed of calcium titanate (chemical formula ). Its name is also applied to the class of compounds which have the same type of crystal structure as (XIIA2+VIB4+X2−3), known a ...
-related material that proved promising and stimulated the search for related compounds with higher superconducting transition temperatures. In 1987, Bednorz and Müller were jointly awarded the Nobel Prize in Physics for this work. Following Bednorz and Müller's discovery, a team at the
University of Alabama in Huntsville The University of Alabama in Huntsville (UAH) is a public research university in Huntsville, Alabama. The university is accredited by the Southern Association of Colleges and Schools and comprises nine colleges: arts, humanities & social scienc ...
and
University of Houston The University of Houston (UH) is a public research university in Houston, Texas. Founded in 1927, UH is a member of the University of Houston System and the university in Texas with over 47,000 students. Its campus, which is primarily in s ...
discovered that YBCO has a superconducting transition critical temperature (''T''c) of 93 K. The first samples were Y1.2 Ba0.8 Cu O4, but this was an average composition for two phases, a black and a green one. Workers at the
Carnegie Institution of Washington The Carnegie Institution of Washington (the organization's legal name), known also for public purposes as the Carnegie Institution for Science (CIS), is an organization in the United States established to fund and perform scientific research. Th ...
found that the black phase (which turned out to be the superconductor) had the composition YBa2Cu3O7−δ. YBCO was the first material found to become superconducting above 77 K, the boiling point of liquid nitrogen, whereas the majority of other superconductors require more expensive cryogens. Nonetheless, YBCO and its many related materials have yet to displace superconductors requiring
liquid helium Liquid helium is a physical state of helium at very low temperatures at standard atmospheric pressures. Liquid helium may show superfluidity. At standard pressure, the chemical element helium exists in a liquid form only at the extremely low temp ...
for cooling.


Synthesis

Relatively pure YBCO was first synthesized by heating a mixture of the metal carbonates at temperatures between 1000 and 1300 K. :4 BaCO3 + Y2(CO3)3 + 6 CuCO3 + (1/2−''x'') O2 → 2 YBa2Cu3O7−''x'' + 13 CO2 Modern syntheses of YBCO use the corresponding oxides and nitrates. The superconducting properties of YBa2Cu3O7−''x'' are sensitive to the value of ''x'', its oxygen content. Only those materials with 0 ≤ ''x'' ≤ 0.65 are superconducting below ''T''c, and when ''x'' ~ 0.07, the material superconducts at the highest temperature of 95 K, or in highest magnetic fields: 120  T for B perpendicular and 250 T for B parallel to the CuO2 planes. In addition to being sensitive to the stoichiometry of oxygen, the properties of YBCO are influenced by the crystallization methods used. Care must be taken to sinter YBCO. YBCO is a crystalline material, and the best superconductive properties are obtained when crystal
grain boundaries In materials science, a grain boundary is the interface between two grains, or crystallites, in a polycrystalline material. Grain boundaries are two-dimensional defects in the crystal structure, and tend to decrease the electrical and thermal ...
are aligned by careful control of annealing and
quenching In materials science, quenching is the rapid cooling of a workpiece in water, oil, polymer, air, or other fluids to obtain certain material properties. A type of heat treating, quenching prevents undesired low-temperature processes, such as pha ...
temperature rates. Numerous other methods to synthesize YBCO have developed since its discovery by Wu and his co-workers, such as chemical vapor deposition (CVD), sol-gel, and aerosol methods. These alternative methods, however, still require careful sintering to produce a quality product. However, new possibilities have been opened since the discovery that trifluoroacetic acid ( TFA), a source of fluorine, prevents the formation of the undesired
barium carbonate Barium carbonate is the inorganic compound with the formula BaCO3. Like most alkaline earth metal carbonates, it is a white salt that is poorly soluble in water. It occurs as the mineral known as witherite. In a commercial sense, it is one of ...
(BaCO3). Routes such as CSD (chemical solution deposition) have opened a wide range of possibilities, particularly in the preparation of long YBCO tapes. This route lowers the temperature necessary to get the correct phase to around 700 °C. This, and the lack of dependence on vacuum, makes this method a very promising way to get scalable YBCO tapes.


Structure

YBCO crystallizes in a defect
perovskite structure A perovskite is any material with a crystal structure following the formula ABX3, which was first discovered as the mineral called perovskite, which consists of calcium titanium oxide (CaTiO3). The mineral was first discovered in the Ural mou ...
consisting of layers. The boundary of each layer is defined by planes of square planar CuO4 units sharing 4 vertices. The planes can sometimes be slightly puckered. Perpendicular to these CuO4 planes are CuO2 ribbons sharing 2 vertices. The
yttrium Yttrium is a chemical element with the symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and has often been classified as a " rare-earth element". Yttrium is almost always found in co ...
atoms are found between the CuO4 planes, while the barium atoms are found between the CuO2 ribbons and the CuO4 planes. This structural feature is illustrated in the figure to the right. Although YBa2Cu3O7 is a well-defined chemical compound with a specific structure and stoichiometry, materials with fewer than seven oxygen atoms per formula unit are
non-stoichiometric compound In chemistry, non-stoichiometric compounds are chemical compounds, almost always solid inorganic compounds, having elemental composition whose proportions cannot be represented by a ratio of small natural numbers (i.e. an empirical formula); m ...
s. The structure of these materials depends on the oxygen content. This non-stoichiometry is denoted by the x in the chemical formula YBa2Cu3O7−''x''. When ''x'' = 1, the O(1) sites in the Cu(1) layer are vacant and the structure is
tetragonal In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a squar ...
. The tetragonal form of YBCO is insulating and does not superconduct. Increasing the oxygen content slightly causes more of the O(1) sites to become occupied. For ''x'' < 0.65, Cu-O chains along the ''b'' axis of the crystal are formed. Elongation of the ''b'' axis changes the structure to orthorhombic, with lattice parameters of ''a'' = 3.82, ''b'' = 3.89, and ''c'' = 11.68 Å. Optimum superconducting properties occur when ''x'' ~ 0.07, i.e., almost all of the O(1) sites are occupied, with few vacancies. In experiments where other elements are substituted on the Cu and Ba sites, evidence has shown that conduction occurs in the Cu(2)O planes while the Cu(1)O(1) chains act as charge reservoirs, which provide carriers to the CuO planes. However, this model fails to address superconductivity in the homologue Pr123 (
praseodymium Praseodymium is a chemical element with the symbol Pr and the atomic number 59. It is the third member of the lanthanide series and is considered to be one of the rare-earth metals. It is a soft, silvery, malleable and ductile metal, valued for i ...
instead of yttrium). This (conduction in the copper planes) confines conductivity to the ''a''-''b'' planes and a large anisotropy in transport properties is observed. Along the ''c'' axis, normal conductivity is 10 times smaller than in the ''a''-''b'' plane. For other
cuprate Cuprate loosely refers to a material that can be viewed as containing anionic copper complexes. Examples include tetrachloridocuprate ( uCl4sup>2−), the superconductor YBa2Cu3O7, and the organocuprates (e.g., dimethylcuprate u(CH3)2sup> ...
s in the same general class, the anisotropy is even greater and inter-plane transport is highly restricted. Furthermore, the superconducting length scales show similar anisotropy, in both penetration depth (λab ≈ 150 nm, λc ≈ 800 nm) and coherence length, (ξab ≈ 2 nm, ξc ≈ 0.4 nm). Although the coherence length in the ''a''-''b'' plane is 5 times greater than that along the ''c'' axis it is quite small compared to classic superconductors such as niobium (where ξ ≈ 40 nm). This modest coherence length means that the superconducting state is more susceptible to local disruptions from interfaces or defects on the order of a single unit cell, such as the boundary between twinned crystal domains. This sensitivity to small defects complicates fabricating devices with YBCO, and the material is also sensitive to degradation from humidity.


Proposed applications

Many possible applications of this and related high temperature superconducting materials have been discussed. For example, superconducting materials are finding use as
magnets A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel ...
in magnetic resonance imaging,
magnetic levitation Magnetic levitation (maglev) or magnetic suspension is a method by which an object is suspended with no support other than magnetic fields. Magnetic force is used to counteract the effects of the gravitational force and any other forces. The ...
, and
Josephson junction In physics, the Josephson effect is a phenomenon that occurs when two superconductors are placed in proximity, with some barrier or restriction between them. It is an example of a macroscopic quantum phenomenon, where the effects of quantum mec ...
s. (The most used material for power cables and magnets is
BSCCO Bismuth strontium calcium copper oxide (BSCCO, pronounced ''bisko''), is a type of cuprate superconductor having the generalized chemical formula Bi2 Sr2 Ca''n''−1 Cu''n'' O2''n''+4+''x'', with ''n'' = 2 being the most commonly stud ...
.) YBCO has yet to be used in many applications involving superconductors for two primary reasons: *First, although single crystals of YBCO have a very high critical current density,
polycrystal A crystallite is a small or even microscopic crystal which forms, for example, during the cooling of many materials. Crystallites are also referred to as grains. Bacillite is a type of crystallite. It is rodlike with parallel longulites. Stru ...
s have a very low critical current density: only a small current can be passed while maintaining superconductivity. This problem is due to crystal
grain boundaries In materials science, a grain boundary is the interface between two grains, or crystallites, in a polycrystalline material. Grain boundaries are two-dimensional defects in the crystal structure, and tend to decrease the electrical and thermal ...
in the material. When the grain boundary angle is greater than about 5°, the supercurrent cannot cross the boundary. The grain boundary problem can be controlled to some extent by preparing thin films via CVD or by texturing the material to align the grain boundaries. *A second problem limiting the use of this material in technological applications is associated with processing of the material. Oxide materials such as this are brittle, and forming them into superconducting wires by any conventional process does not produce a useful superconductor. (Unlike
BSCCO Bismuth strontium calcium copper oxide (BSCCO, pronounced ''bisko''), is a type of cuprate superconductor having the generalized chemical formula Bi2 Sr2 Ca''n''−1 Cu''n'' O2''n''+4+''x'', with ''n'' = 2 being the most commonly stud ...
, the
powder-in-tube Superconducting wires are electrical wires made of superconductive material. When cooled below their transition temperatures, they have zero electrical resistance. Most commonly, conventional superconductors such as niobium-titanium are used, ...
process does not give good results with YBCO.) The most promising method developed to utilize this material involves deposition of YBCO on flexible metal tapes coated with buffering metal oxides. This is known as . Texture (crystal plane alignment) can be introduced into the metal tape (the RABiTS process) or a textured ceramic buffer layer can be deposited, with the aid of an ion beam, on an untextured alloy substrate (the
IBAD The ʿIbād or ʿEbād () were a Christian Arab group within the city of al-Ḥīra (Ḥirtā) during Late Antiquity and the early Middle Ages, when the city was part of the Sasanian Empire and later the Caliphate. Of diverse tribal backgrounds, ...
process). Subsequent oxide layers prevent diffusion of the metal from the tape into the superconductor while transferring the template for texturing the superconducting layer. Novel variants on CVD, PVD, and solution deposition techniques are used to produce long lengths of the final YBCO layer at high rates. Companies pursuing these processes include
American Superconductor American Superconductor (AMSC) is an American energy technologies company based in Ayer, Massachusetts specializing in the design and manufacture of power systems and superconducting wire. It owns AMSC Windtech in Klagenfurt, Austria. Detroit ...
, Superpower (a division of
Furukawa Electric is a Japanese electric and electronics equipment company. The company was founded by Furukawa Ichibei in 1884 in Yokohama when a copper-smelting facility and a wire manufacturing factory were established. Furukawa was a Japanese businessman w ...
), Sumitomo,
Fujikura is a global, Tokyo-based electrical equipment manufacturing company, developing and manufacturing power and telecommunication systems products, including devices for optical fibers, such as cutters and splicers. Fujikura was founded by Zenpach ...
, Nexans Superconductors, Commonwealth Fusion Systems, and European Advanced Superconductors. A much larger number of research institutes have also produced YBCO tape by these methods. The superconducting tape may be the key to a
tokamak A tokamak (; russian: токамáк; otk, 𐱃𐰸𐰢𐰴, Toḳamaḳ) is a device which uses a powerful magnetic field to confine plasma in the shape of a torus. The tokamak is one of several types of magnetic confinement devices being ...
fusion reactor design that can achieve breakeven energy production. YBCO is often categorized as a
rare-earth barium copper oxide Rare-earth barium copper oxide (also referred to as ReBCO) is a family of chemical compounds known for exhibiting high temperature superconductivity (HTS). ReBCO superconductors have the potential to sustain stronger magnetic fields than other s ...
(REBCO).


Surface modification

Surface modification of materials has often led to new and improved properties. Corrosion inhibition, polymer adhesion and nucleation, preparation of organic superconductor/insulator/high-''T''c superconductor trilayer structures, and the fabrication of metal/insulator/superconductor tunnel junctions have been developed using surface-modified YBCO. These molecular layered materials are synthesized using
cyclic voltammetry Cyclic voltammetry (CV) is a type of potentiodynamic electrochemical measurement. In a cyclic voltammetry experiment, the working electrode potential is ramped linearly versus time. Unlike in linear sweep voltammetry, after the set potential is r ...
. Thus far, YBCO layered with alkylamines, arylamines, and
thiol In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl gro ...
s have been produced with varying stability of the molecular layer. It has been proposed that amines act as
Lewis bases A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any s ...
and bind to Lewis acidic Cu surface sites in YBa2Cu3O7 to form stable
coordination bond In coordination chemistry, a coordinate covalent bond, also known as a dative bond, dipolar bond, or coordinate bond is a kind of two-center, two-electron covalent bond in which the two electrons derive from the same atom. The bonding of metal io ...
s.


Mass production

In 2021, SuperOx, a Russian and Japanese company, developed a new manufacturing process for making YBCO wire for fusion reactors. This new wire was shown to conduct between 700 and 2000 Amps per square millimeter. The company was able to produce 186 miles of wire in 9 months, between 2019 and 2021, dramatically improving the production capacity. The company used a plasma-laser deposition process, on a electropolished substrate to make 12-mm width tape and then splice it into 3-mm tape.


Hobbyist use

Shortly after it was discovered, physicist and science author Paul Grant published in the U.K. Journal ''
New Scientist ''New Scientist'' is a magazine covering all aspects of science and technology. Based in London, it publishes weekly English-language editions in the United Kingdom, the United States and Australia. An editorially separate organisation publish ...
'' a straightforward guide for synthesizing YBCO superconductors using widely-available equipment. Thanks in part to this article and similar publications at the time, YBCO has become a popular high-temperature superconductor for use by hobbyists and in education, as the magnetic levitation effect can be easily demonstrated using liquid nitrogen as coolant.


References


External links


Diagram of YBCO structure
* ttp://www.futurescience.com/manual/ybcomsds.html External MSDS Data Sheet (safety classifications) for YBCO
Superconductivity in everyday life : Interactive exhibition – little if any specific to YBCO
. {{DEFAULTSORT:Yttrium Barium Copper Oxide Yttrium compounds Barium compounds Copper compounds High-temperature superconductors Mixed valence compounds Transition metal oxides Non-stoichiometric compounds Articles containing video clips Ceramic materials