Oxy-anion substitutions in the system [Y/Ce] ₂ Sr 2–x Ba x Cu ₃ O 9–y

The partial substitution of oxy-anions for the Cu in the ‘chain’ sites in the system [Y/Ce]2Sr2–xBaxCu3O9–y has been examined, and the successful substitution of borate, phosphate and sulphate groups at these sites has been achieved. The highest substitution level (80% replacement of the ‘chain’ Cu sites) occurred for borate ions and was associated with a significant reduction in the unit-cell c-axis length. For phosphate and sulfate groups, however, the maximum substitution level corresponded to only 25% of the ‘chain’ Cu sites. None of the samples prepared showed any evidence for superconductivity.