Bending stress- and magnetic field-dependence of I_c in JFCA-RRT samples

Japan Fine Ceramics Association has carried out a round robin test (RRT) on the bending strain (_b) dependence of the critical current I_c at 77 K in three kinds of Bi(2223)/Ag tape samples (VAM-1, JFC-1, JFC-2; three samples each) for future standardization. We measured I_c(_b) (_b: 0-1.0%) as one of RRT participants and also measured the magnetic field dependence of I_c under several bending strains mentioned above as optional measurements. As results, we found a very fast decrease of I_c in low fields up to 0.5 T and then a gradual decrease up to 1.5-2.0 T. I_c maintains 0.9-0.95 of its initial value up to _b=0.4% strain and then decreases a little faster down to 0.60-0.65 at _b=1.0% for almost all samples and magnetic fields. The normalized pinning force F_p/F_pmax shows scaling according to the expression F_p/F_pmax∝(B/B_irr)(1-(B/B_irr)) ³ for all samples and bending strains, where B_irr is the irreversibility field.