Microstructure and Flux Pinning of Reacted-and-Pressed, Polycrystalline Ba(0.6)K(0.4)Fe(2)As(2) Powders

The flux pinning properties of reacted-and-pressed Ba(0.6)K(0.4)Fe(2)As(2) powder were measured using magnetic hysteresis loops in the temperature range 20 K ≤ T ≤ 35 K. The scaling analysis of the flux pinning forces ([Formula: see text] , with [Formula: see text] denoting the critical current density) following the Dew-Hughes model reveals a dominant flux pinning provided by normal-conducting point defects ([Formula: see text]-pinning) with only small irreversibility fields, [Formula: see text] , ranging between 0.5 T (35 K) and 16 T (20 K). Kramer plots demonstrate a linear behavior above an applied field of 0.6 T. The samples were further characterized by electron backscatter diffraction (EBSD) analysis to elucidate the origin of the flux pinning. We compare our data with results of Weiss et al. (bulks) and Yao et al. (tapes), revealing that the dominant flux pinning in the samples for applications is provided mainly by grain boundary pinning, created by the densification procedures and the mechanical deformation applied.