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Title: Study of grain boundary transparency in(Yb$$_{1-x}$$Ca$$_x$$)Ba$$_2$$Cu$$_3$$O bicrystal thin films over a wide temperature, field, and field orientation range

Abstract

The residual low angle grain boundary (GB) network is still the most important current-limiting mechanism operating in bi-axially textured rare earth barium copper oxide (REBCO) coated conductors. While Ca-doping is well established to improve super-current flow across low angle GBs in weak fields at high temperatures, Ca-doping also depresses T c, making it so far impractical for high temperature applications of REBCO coated conductors. On the other hand, high field magnet applications of REBCO require low temperatures. Here we systematically evaluate the effectiveness of Ca-doping in improving the GB transparency, r GB= J c GB/J c grain, of low angle Yb 1-xCa xBaCuO [001] tilt bi-crystal films down to 10K and with magnetic fields perpendicular and parallel to the film surfaces, while varying the Ca and oxygen doping level. Using Low Temperature Scanning Laser Microscopy (LTSLM) and Magneto-Optical Imaging (MOI), we found r GB to strongly depend on the angle between magnetic field and the GB plane and clearly identified regimes in which J c GB can exceed J c grain (rGB>1) where the GB pinning is optimized by the field being parallel to the GB dislocations. However, even in this favorable situation, we found that r GB became muchmore » smaller at lower temperatures. Calculations of the GB Ca segregation profile predict that the high J c channels between the GB dislocation cores are almost Ca-free. It may be therefore that the positive effects of Ca doping seen by many authors near T c are partly a consequence of the higher Tc of these Ca-free channels.« less

Authors:
 [1];  [2];  [2];  [2];  [2]
  1. Fermilab
  2. Natl. High Mag. Field Lab.
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1419019
Report Number(s):
arXiv:1504.07861; FERMILAB-PUB-15-679-TD
Journal ID: ISSN 2469-9950; PRBMDO; 1624634
DOE Contract Number:  
AC02-07CH11359
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review B; Journal Volume: 91; Journal Issue: 10
Country of Publication:
United States
Language:
English

Citation Formats

Li, Pei, Abraimov, Dmytro, Polyanskii, Anatolii, Kametani, Fumitake, and Larbalestier, David. Study of grain boundary transparency in(Yb$_{1-x}$Ca$_x$)Ba$_2$Cu$_3$O bicrystal thin films over a wide temperature, field, and field orientation range. United States: N. p., 2015. Web. doi:10.1103/PhysRevB.91.104504.
Li, Pei, Abraimov, Dmytro, Polyanskii, Anatolii, Kametani, Fumitake, & Larbalestier, David. Study of grain boundary transparency in(Yb$_{1-x}$Ca$_x$)Ba$_2$Cu$_3$O bicrystal thin films over a wide temperature, field, and field orientation range. United States. doi:10.1103/PhysRevB.91.104504.
Li, Pei, Abraimov, Dmytro, Polyanskii, Anatolii, Kametani, Fumitake, and Larbalestier, David. Fri . "Study of grain boundary transparency in(Yb$_{1-x}$Ca$_x$)Ba$_2$Cu$_3$O bicrystal thin films over a wide temperature, field, and field orientation range". United States. doi:10.1103/PhysRevB.91.104504. https://www.osti.gov/servlets/purl/1419019.
@article{osti_1419019,
title = {Study of grain boundary transparency in(Yb$_{1-x}$Ca$_x$)Ba$_2$Cu$_3$O bicrystal thin films over a wide temperature, field, and field orientation range},
author = {Li, Pei and Abraimov, Dmytro and Polyanskii, Anatolii and Kametani, Fumitake and Larbalestier, David},
abstractNote = {The residual low angle grain boundary (GB) network is still the most important current-limiting mechanism operating in bi-axially textured rare earth barium copper oxide (REBCO) coated conductors. While Ca-doping is well established to improve super-current flow across low angle GBs in weak fields at high temperatures, Ca-doping also depresses Tc, making it so far impractical for high temperature applications of REBCO coated conductors. On the other hand, high field magnet applications of REBCO require low temperatures. Here we systematically evaluate the effectiveness of Ca-doping in improving the GB transparency, rGB= JcGB/Jcgrain, of low angle Yb1-xCaxBaCuO [001] tilt bi-crystal films down to 10K and with magnetic fields perpendicular and parallel to the film surfaces, while varying the Ca and oxygen doping level. Using Low Temperature Scanning Laser Microscopy (LTSLM) and Magneto-Optical Imaging (MOI), we found rGB to strongly depend on the angle between magnetic field and the GB plane and clearly identified regimes in which JcGB can exceed Jcgrain (rGB>1) where the GB pinning is optimized by the field being parallel to the GB dislocations. However, even in this favorable situation, we found that rGB became much smaller at lower temperatures. Calculations of the GB Ca segregation profile predict that the high Jc channels between the GB dislocation cores are almost Ca-free. It may be therefore that the positive effects of Ca doping seen by many authors near Tc are partly a consequence of the higher Tc of these Ca-free channels.},
doi = {10.1103/PhysRevB.91.104504},
journal = {Physical Review B},
number = 10,
volume = 91,
place = {United States},
year = {Fri Mar 06 00:00:00 EST 2015},
month = {Fri Mar 06 00:00:00 EST 2015}
}