Synthesis of ultrafine Y2BaCuO5 powder and its incorporation into YBCO bulk by powder melting process

A solid state sintering process for the synthesis of ultrafine Y2BaCuO5 pre cursor has been developed and YBCO bulk samples containing Y2BaCuO5 particl es less than 500 nm in diameter have been prepared successfully by powder m elting process (PMP), The solid state sintering process consists of two ste ps: firstly, BaCuO2 powder was synthesized by calcining the mixture of BaCO 3 and CuO powders; secondly, BaCuO2 powder was well mixed with commercial Y 2O3 in a molar ratio of 1:1, and sintered at 900 degreesC for 14 h in flowi ng oxygen. After ball milling, ultrafine Y2BaCuO5 powder with an average di ameter below 0.5 mum was produced. This kind of ultrafine Y2BaCuO5 powder w as used as precursor and quasi-single crystal YBCO samples with a nominal c omposition of YBa2Cu3O6+delta + 15 wt.% excess Y2BaCuO5 + 0.5 wt.% CeO2 wer e prepared by PMP. Y2BaCuO5 particles less than 500 nm in diameter were fou nd within textured YBCO matrix. A high density of twins with an average spa cing of about 60-80 nm was also observed. Magnetization measurements have b een performed on the sample and critical current densities (Jj have been ca lculated based on the extended Bean critical state model. The sample exhibi ts J(c) values of 4.57 x 10(6) and 1.85 x 10(5) A/cm(2) in 1 T magnetic fie ld at 20 and 77 K, respectively. Such high J(c) values are attributed to th e fine 211 particles and related defects. (C) 2001 Elsevier Science B.V. Al l rights reserved.