New procedure for determination of [Cu-O]^+p charge and oxygen content in high T_c copper oxides

The properties of High Tc Superconductors are critically dependent on the degree of oxidation, i.e., on the average [Cu-O]+p charge (or formal oxidation state Cu+2+p of copper). This fact makes it important to accurately characterize High Tc copper oxide samples in term of this key parameter. We describe here a simple and reliable procedure for determining the effective copper oxidation level and, as a result, the oxygen content. Using a modification of standard iodometric titration techniques, our procedure involves the ratio of the results of two titrations: one to determine the copper concentration in the sample and the second to measure the degree of oxidation beyond Cu+. Using this ratio, numerous errors and difficulties are minimized. In addition, the exact stoichiometry of the sample need not be known. Experimental results on YBa2Cu3Oy are discussed which demonstrate the accuracy, reproducibility and reliability of our procedure. © 1988, Elsevier Science Publishers B.V.. All rights reserved.