Preparation of conducting In-based copper oxide by annealing under high pressure

By annealing InBa2CuO4.44 in oxygen at a pressure of 60MPa, a new conducting cuprate InBa2CuO4.54 with having a- and c-axis lengths of 4.190A and 8.363A was formed. Its crystal structure was refined by the X-ray Rietveld analysis method. The factors Rwp, Re, and S were 9.11%, 9.12%, and 1.0, respectively, indicating that the refined structure is an appropriate one. There were four distinct differences between InBa2CuO4.44 and InBa2CuO4.54. The first was an increase in the oxygen occupancy in the CuO2 plane; the oxygen occupancy in the CuO2 plane increased from 26.5% to 27%. The second was a drastic increase in the c-axis length from 8.09A to 8.36A. The third was the inter-substitution of In and Cu. About 35% of In and Cu atoms were substituted each other in the InBa2CuO4.54. The fourth was a drastic decrease in the electrical resistivity; the resistivity at room temperature decreased from 28.8MΩcm to 90.3kΩcm. These differences are discussed in connection with the oxygen content in the InBa2CuOy. (author)