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 degrees. Smaller specimens cut from the bars were deformed under flowing oxygen in the temperature range 850-950 degrees C applying strain rates from 1x10(-5) to 5 x 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 (n(D) > 10(9) 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. (C) 1998 Elsevier Science S.A. All rights reserved.