STRUCTURAL CHANGES OF Ni-DOPED YBCO AT DIFFERENT TEMPERATURE

Abstract

In YBa 2 Cu 3-x Ni x O y at about 480°C all the samples show a tetragonal phase. Comparing the structural changes at 480°C with those at room temperature, the bond lengths such as Cu (1)- O (4) and Cu (2)- O (4) vary regularly with Ni -content increasing at room temperature, but not at high temperature. It suggests that there is a close correlation between structural changes and superconductivity in this system. The difference of orthorhombic- tetragonal phase -transition is also discussed between undoped YBCO and Ni -doped YBCO at high temperature.