Fabrication and sintering characteristics of doctor blade YBCO-Ag tapes

A detailed study of the fabrication and thermolysis behaviour of YBCO-Agx (x=0.1) tapes cast by doctor blade technique was carried out. During thermolysis, anisotropic shrinkage along the length and thickness of the tapes was observed due to the anisotropic nature of the capillary force acting on the particles during volatilization of the solvent, binder and plasticizer. The sintering study also revealed anisotropic behaviour along the thickness and length of the tapes. From the shrinkage and densification studies, the average activation energy was estimated to be ≈150 kJ/mol. However, it appears that two stages of sintering mechanisms operate one below ∼1050 K (activation energy, Q=52±0.5 kJ/mol) and the other above 1050 K (Q=301±6 kJ/mol). Enhanced grain-growth after achieving a densification of 80% of the theoretical density was noticed. The sintering studies of the tapes along their thickness resulted in an apparent activation energy for sintering as 816±69 kJ/mol above 1193 K. Scanning electron microscopy studies indicated the possibility of liquid phase sintering above 1193 K, which was the cause of high activation energy.