High temperature deformation of Bridgman melt-textured YBCO

Large bars were melt-textured using a modified Bridgman method. Neutron diffraction analysis revealed the absence of any large angle grain boundary and a FWHM of < 6 °. Smaller specimens cut from the bars were deformed under flowing oxygen in the temperature range 850–950 °C applying strain rates from 1 × 10−5 to 5 × 10−4 s−1. These high temperature deformation experiments reveal that the predominant deformation mechanism is dislocation glide and climb controlled by climb at Y-211 particles and that no significant grain boundary sliding occurs. TEM investigations support a deformation mechanism based on dislocation movement, i.e. the dislocation density of the deformed samples is 2–3 orders of magnitude larger (nd > 109 cm−2) than that of undeformed samples. Critical current density measurements clearly follow the induced microstructural changes. An improvement of the mechanical properties is expected by introducing a bimodal Y-211 distribution.