MICROSTRUCTURE OF THE DOMAIN BOUNDARY AND THE EFFECT OF EXCESS CUO IN THE MELT-TEXTURED Y-BA-CU-O OXIDES

Microstructures near the domain boundary were investigated in the YBa2Cu3O7-y(Y123) samples melt-textured in air atmosphere. It is found that the free CuO phase is often observed near the domain boundaries of the Y123 samples, probably due to the variation of the composition of the finally solidified liquid phase. Also, the effect of excess CuO on the microstructure of the domain boundary was investigated in the Y123 melt-textured with 5 wt.%-20 wt.% CuO addition. When the amount of the CuO is small, CuO phase exists as a discrete form at the domain boundaries. As the CuO content increases, spherical CuO pockets and large CuO pools containing unreacted Y211 particles are developed. In addition, the CuO addition changes the growth morphology of the Y123 domain; from a planar mode to a Y123/CuO cellular structure with increasing CuO content.