Joseph Fourier – Grenoble Northwestern Polytechnical University – Xi

A series of fruitful results were achieved in the course of our study on the fabrication of superconductor YBCO single domain by Powder Melting Process (PMP). First, by the high temperature Faraday Balance, we revealed the dynamic phase transition in the growth of YBCO single domain in PMP process, which is an original research work in this field. The clear phase transition results build a fundamental understanding for fabricating YBCO single domain by the PMP process. Second, we studied the growth dynamics of PMP-YBCO single domain. The effect of oxygen diffusion is underlined on the growth rate of YBCO single domain. From the relationship of growth rate and the undercooling study, we deduce that the YBCO crystal growth depends on two types of diffusion. One relates to the yttrium, barium and copper ions transport to the 123 growth interface through the melt liquid by solution diffusion and interfacial diffusion as in melt-solid system. The other one concerns the oxygen diffusion which relies on interfacial diffusion from air as in vapor-solid system. Finally, we were first to successfully fabricate the Ф30mm×15mm YBCO single domain in batch with PMP process. A large trapped magnetic field value of Btr=739mT was obtained in a Φ15mm hole YBCO single domain. A record magnetic critical current density Jcm~1.2×10A/cm (77K) was achieved. The obtained results give us more confidence to fabricate high quality YBCO single domain samples.