Flux Pinning Enhancement of YBCO Films by Y and Ba Site Doping at Minute Concentrations
- PDF / 153,094 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 45 Downloads / 166 Views
1001-M13-03
Flux Pinning Enhancement of YBCO Films by Y and Ba Site Doping at Minute Concentrations Joseph W. Kell, and Paul N. Barnes AFRL/PRPG, US Air Force Research Laboratory, 2645 Fifth St., Bldg. 450, Wright-Patterson AFB, OH, 45433-7919
ABSTRACT YBa2Cu3O7-x (Y123) superconducting thin films can maintain high critical current densities in applied magnetic fields up to a few Tesla at 77 K. Even so, this does not preclude the intentional addition of alternate flux pinning centers in the Y123 films to further optimize their in-field Jc. Unfortunately, many methods to incorporate flux pinning centers into Y123 thin films introduce additional steps and/or re-optimization of the deposition parameters for a given addition. Identifying potential additions that can optimize the performance of YBCO films without changing the deposition conditions would be ideal. The work presented here is an extension of earlier work and demonstrates new dopants and possibilities for introducing pinning centers by the route of minute doping or nanodoping. Preliminary results of a study to determine if minute doping can be performed with smaller lanthanide atoms (Tm, Lu), non-lanthanide atoms (Sc) and Ba-site substitution (Sr) are presented. All samples were deposited under identical conditions as pure YBCO. The new dopants will be discussed in addition to those previously presented (Tb, Pr, Ce, Nd, and La). Critical current density data will be presented for 65 K and 77 K in fields up to 9T in addition to new structural data obtained by cross-sectional TEM. INTRODUCTION YBa2Cu3O7-d (Y123) coated conductors on buffered metallic substrate are currently the primary candidate for second generation high temperature superconducting (HTS) coated conductor for a variety of power applications. Possible applications include motors and generators, which will subject the Y123 to large magnetic fields and suppress the performance of Y1231. Self-field critical current densities (Jc) of around ~106 A/cm2 at 77 K are regularly attained in YBCO thin films but magnetic fields in excess of 1 T applied along the c-axis direction tend to depress the Jc(H) (infield critical current density) by an order of magnitude or more. Therefore, improvement of the infield properties of the Y123 film is critical to enable high field applications and to minimize the size and weight of future power systems. A common method of achieving the desired Jc(H) values is to incorporate well-dispersed, artificial, magnetic flux pinning centers into the YBCO lattice2-7. These pinning centers can consist of nonsuperconducting particulates2-4 or secondary superconducting phases5-6. Doping Y123 with rare earth (RE) elements may lead to the formation of both types of particulate pinning centers as well as additional pinning centers caused by defects in the crystal lattice. Nonsuperconducting particulates form when the RE elements react to form a nonsuperconducting phase (e.g. Y substitution by Ce or Pr), while secondary superconducting phases form when other RE elements substitute fo
Data Loading...
