Intragrain pinning strength depth dependence of 2223-(Bi,Pb)-based high critical Tc ceramics made by a vitreous route

Campbell's method for measuring the critical current in superconductors has been used to obtain the critical current density and the pinning strength in Bi1.7Pb0.3Sr2Ca2Cu3O10−y ceramics synthesized by a vitreous route. The intragrain critical current is much higher than 10^5 A/cm2 at 40 K in zero dc magnetic field. A large increase of the pinning strength is observed near the grain surface. The decrease with depth is hyperbolic. The role of the precursors in the synthesis route is emphasized for introducing specific pinning centers. The analysis takes into consideration the ceramics granular nature, i.e., the existence of intergrain and intragrain currents. ©1995 American Institute of Physics.