YBCO COATED CONDUCTORS
- ORNL
Since the discovery of high-temperature superconductors (HTS) in 1986, both (Bi,Pb)2Sr2Ca2Cu3O10 (BSCCO or 2223 with a critical temperature, Tc of 110 K) and YBa2Cu3O7- (YBCO or 123 with a Tc of 91 K) have emerged as the leading candidate materials for the first generation (1G) and second generation (2G) high temperature superconductor wires or tapes that will carry high critical current density in liquid nitrogen temperatures [1-7]. The crystal structures and detailed fundamental properties of BSCCO and YBCO superconductors have been reviewed by Matsumoto in a separate chapter in this book. The U.S. Department of Energy s target price for the conductor is close to the current copper wire cost of $10-50/kA-meter, i.e. a meter of copper type conductor carrying 1000 A current costs ~ $ 50 [8]. The long-term goal for the DOE, Office of Electricity, Advanced Conductors and Cables program is to achieve HTS wire in 1000 meters long with current carrying capacity of 1000 A/cm [8]. Robust, high-performance HTS wire will certainly revolutionize the electric power grid and various other electric power equipments as well. Sumitomo Electric Power (Japan) has been widely recognized as the world leader in manufacturing the first-generation HTS wires based on BSCCO materials using the Oxide-Powder-In-Tube (OPIT) over-pressure process [9]. Typically, 1G HTS wires carry critical currents, Ic, of over 200 Amperes (A) in piece lengths of one kilometer lengths at the standard 4 mm width and ~ 200 m thickness. However, due to the higher cost of 1G wire, mainly because of the cost of Ag alloy sheath, the researchers shifted their effort towards the development of YBCO (second generation 2G) tapes in the last fifteen years [1-7]. One of the main obstacles to the ability to carry high critical currents in YBCO films has been the phenomenon of weak links, i.e., grain boundaries formed by the misalignment of neighboring YBCO grains are known to form obstacles to current flow [10]. By carefully aligning the grains in YBCO films, low angle boundaries between superconducting YBCO grains allow more current to flow. In fact below a critical misalignment angle of 4 , the critical current density approaches that of YBCO films grown on single crystal substrates [10]. Typically, 2G HTS wires have three components, flexible metal substrate, buffer layers, and REBa2Cu3O7- (REBCO: RE = Rare Earth) superconductor layers [1-7]. Several methods were developed to obtain biaxially textured templates suitable for fabricating high-performance YBCO coated conductors. They are Ion-Beam Assisted Deposition (IBAD), Rolling-Assisted Biaxially Textured Substrates (RABiTS) and Inclined-Substrate Deposition (ISD). Compared to 1G wire, for producing 2G wires using RABiTS or IBAD process, silver is replaced by a low cost nickel alloy, which allows for fabrication of less expensive HTS wires.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- OE USDOE - Office of Electric Transmission and Distribution
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 983826
- Country of Publication:
- United States
- Language:
- English
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