2-STAGE SINTERING OF DENSE SUPERCONDUCTING YBA2CU4O8 CERAMICS

Dense YBa2Cu4O8 (124) ceramics were prepared by the following two-stag e sintering: compressed 124 powders were heated to 1203 K for decompos ition to YBa2Cu3O7-x (123) and CuO, and then cooled down to 1073 K and annealed for the re-formation of 124 single phase. The relative densi ties thus obtained were 93-95%, as high as those prepared under high o xygen pressure. The densification was considered to take place due to the liquid phase, In the sintered 124, the island-like fine grains of CuO were observed within the 123 matrix. As a result, it was considere d that the re-formation of 124 proceeded in each grain. The geometrica l phase distribution in the grains is discussed on the basis of superc onducting properties from resistivity measurements.