RELATIVE CORROSION REACTIVITY AND SURFACE MICROSTRUCTURE OF YBA2CU3O7-X SAMPLES WITH DIFFERENT OXYGEN CONTENTS

The relative chemical reactivity toward water within the YBa2Cu3O7-x series (0 < x < 1) is found to be YBa2Cu3O6.59 < YBa2Cu3O7.00 << YBa2Cu3O6.05. Thus, factors other than copper valence, such as internal strain and lattice vacancies, are likely to be responsible for the high reactivity of the oxygen-deficient phase. For the two orthorhombic samples, YBA2Cu3O7.00 and YBa2Cu3O6.59, the reactivity follows the expected trend based on the copper valence. Additional useful information related to the mechanism of corrosion is acquired from an examination of the surface microstructure of water-degraded YBa2Cu3O7-x samples. Accordingly, inter- and intragrain cracking phenomena occur during water degradation of YBa2Cu3O7-x specimens and serve to enhance the rate of decomposition of the high-T(c) lattice. Interestingly, the surface microstructure of corroded samples reveals features which appear to be related to the twinning structure of the host lattice.