High pressure/high temperature treatment of melt textured YBCO high temperature superconductors

Bulk cylindrical blocks of YBCO, 30 mm in diameter and 17 mm in thickness, are prepared by a modified Melt Textured Growth batch process. Blocks are consisting of weak textured 1-2 cm³ grains. Samples with dimensions of about (8×8×5) mm³ are cutted from the blocks, encapsulated in ZrO ₂and inserted in a recessed anvil-type high pressure apparatus assembly for high pressure (1-5 GPa)/high temperature (700-950°C) treatment (HP-HT) under quasi isostatic conditions. Superconductive and mechanical properties were investigated. By the treatment samples are compacted near to the theoretical density. Structure and mechanical properties are homogenized by the HP-HT treatment. The hermetic treatment results in sample transition temperatures > 90 K with transition width below 2 K (acsusceptibility) comparable to the starting material. By vibration sample magnetometry intra-grain critical current densities before and after treatment are measured. Polarization microscopy show plastically deformed microstructure and reduced twin boundary density.