The preparation of large‐scale YBa2Cu3O7−x superconductor samples was investigated. This method is based on plastic forming using a slurry consisting of YBa2Cu3O7−x particles and a sol solution made up of multimetallic hydroxide particles (YBa2Cu3(OH)x colloidal particles) and poly(vinyl) alcohol (PVA). The effects of adding PVA on the product, the crystallinity, and the superconducting properties of the sample were investigated. It was found that PVA acted as a protective colloid in the sol solution and stabilized YBa2Cu3(OH)x colloidal particles, and that the role of PVA changed from a thickener to a flocculant during drying so that the formability/workability of the green sheet sample was improved and large samples (about 80 mm × 80 mm × 3 mm) without large cracks were obtained after firing. The samples became superconducting at 91.5±0.5 K (Tcon) and the full transition temperature (Tcoff) was 88.5±1.5 K. The critical current density (Jc) of the sample prepared from the slurry containing 1 wt% PVA was 713±150 A/cm2 at 77 K. This Jc value was improved to 2300 A/cm2 by heat treatment at 773 K under an oxygen atmosphere.

The large bulk high-T c YBa 2 Cu 3 O 7Àx (YBCO) superconductor samples were prepared by plastic-forming method. We examined the effects of the solvent and the crystallinity of YBCO powder on the composition, crystallinity, and superconducting properties of YBCO sheet samples (sample size: 50 mm 3 50 mm 3 3 mm). By changing the solvent from water to turpentine oil, the leaching of Ba 2+ ions from YBa 2 Cu 3 (OH) y multimetallic hydroxide particles used as an inorganic binder and the YBCO powder were reduced. This results in the composition of the grain boundaries of fired YBCO sheet samples to be the same as the composition of YBa 2 Cu 3 (OH) y multimetallic hydroxide particles. Changing nondoped YBCO powder prepared by sintering to 5 wt% Pt-doped YBCO powder prepared by melt texturing, J c value of YBCO sheet samples changed from about 700 to 6,106 A/cm 2 at 77 K.