A study of high-Tc superconductivity in the Nd-Ba-Cu-O system

The purpose of this study was to investigate superconductivity in the Nd-Ba-Cu-O system, and to define any dissimilarity between NdBa2Cu3Ox and YBa2Cu3Ox compounds. NdBa2Cu3Ox samples were synthesized by a solid-state reaction, which yielded predominantly the 123 phase and showed satisfactory superconducting properties. The phase equilibrium study revealed that there were two ternary compounds (NdBa2Cu3Ox and Nd2BaCuO5) and three binary compounds (Nd2BaO4, Nd2CuO4, and BaCuO2) present in this system. The equilibrium oxygen contents in NdBa2Cu3Ox were found to be dependent on the annealing temperature and oxygen partial pressure. Compared with YBa2Cu3Ox, it had slightly higher oxygen contents, possibly due to the larger unit cell. The enthalpy value associated with the oxidation reaction was about 36-42 Kcal/mole, which was the same as in the YBa2Cu3Ox system. The oxygen contents were found to have strong effects on the sample resistance and the superconducting transition temperature