As a result of improvement on melt/solidification processing, the critical current density (Jc) at 77K of YBCO bulk superconductors has been increased even in a magnetic field. Especially, QMG and MPMG method has become to give a Jc value high enough for practical use. Zonemelting method has been utilized to fabricate superconducting wires. Recently, a single crystal Y 123 has been also continuously fabricated by using a crystal pulling method. The growth mechanism of 123 crystal from the partial molten state is gradually clarified and the special peritectic reaction mechanism has been proposed. Applicable process (e.g. superconductiog wires, magnetic bearing) are expected to be developed.
Specific heats of polyvinylformal, which is insulator for superconducting wires, and carbon for thermometers are measured in the temperature range from 14K to 248K for the former and ranges from 14K to 201K and from 243K to 274K for the latter by an adiabatic calorimeter. Experimental results are represented by 6th- or 7th-polynomial equations with respect to temperature. Specific heats of polyvinylformal above 20K and ones of carbon for thermometers above 50K are precise enough for numerical analysis of the thermal stability on a superconducting coils.