Relative corrosion reactivity and surface microstructure of yttrium barium copper oxide (YBa2Cu3O7-x) samples with different oxygen contents

Abstract

The relative chemical reactivity toward water within the YBa[sub 2]Cu[sub 3]O[sub 7-x] series (O < x < 1) is found to be YBa[sub 2]Cu[sub 3]O[sub 6.59] < YBa[sub 2]Cu[sub 3]O[sub 7.00] << YBa[sub 2]Cu[sub 3]O[sub 6.05]. 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, YBa[sub 2]Cu[sub 3]O[sub 7.00] and YBa[sub 2]Cu[sub 3]O[sub 6.59], 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 YBa[sub 2]Cu[sub 3]O[sub 7-x] samples. Accordingly, inter- and intragrain cracking phenomena occur during water degradation of YBa[sub 2]Cu[sub 3]O[sub 7-x] specimens and serve to enhance the rate of decomposition of the high-[Tc] lattice. Interestingly, the surface microstructure of corroded samples reveals features with appear to be related to the twinning structure of the host lattice. 30 refs., 3 figs., 2 tabs.