Friday, 2E-10, -

Microstructural Study of Strong Vortex Pinning in a Coated Conductor for Use in Specific Fields and Temperatures

Fumitake Kametani

Zhijun Chen, David Larbalestier, Yimin Chen*, Yi-Yuan Xie* and Venkat Selvamanickam*

Applied Superconductivity Center, National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL32301. Author’s e-mail address: Kametani@asc.magnet.fsu.edu *SuperPower Inc. Schenectady, NY 12304

It is still unclear what type, size, shape and distribution of defects and nano particles in a coated conductor are optimum for specific temperatures and fields. Cross-sectional transmission electron microscope has been performed to study the microstructure of the YBCO films and coated conductors (CCs) with defects and nano particles in a different size, shape and distribution and its correlation of vortex pinning at various temperature and fields. The MOCVD CC we examined contains dense ab-plane stacking faults and three-dimensional Y2O3 nanoprecipitates, which are ~12 nm wide and ~6 nm thick and with ~20 nm spacing perpendicular to the film surface. We also made PLD YBCO films containing Y2O3 nanoprecipitates of smaller size and spacing. Although the volume fraction of Y₂O₃ is comparable (~12-15%), the MOCVD CC shows higher H_irr at 77 K, indicating stronger resistance to thermal fluctuations at high fields. However, deconvolution of the strong and weak pinning components of the pinning derived from analysis of the J_c-T curves over a wide range of H and T using the Barcelona group approach indicates a crossover at lower temperatures where the PLD film with smaller nanoprecipitates shows stronger pinning. We are attempting to incorporate thermal fluctuation effects into our description of the optimum pinning nanaostructures.

Download Extended Abstract

Back to the Friday Schedule.