A comparison of the stability of Bi<sub>2</sub>Sr<sub>2</sub>CaCu<sub>2</sub>O<sub>8+y</sub> with YBa<sub>2</sub>Cu<sub>3</sub>O<sub>6.5+y</sub> in various solutions
H K Liu; S X Dou; A J Bourdillon; C C Sorrell; H K Liu; Sch. of Mater. Sci. & Eng., New South Wales Univ., Kensington, NSW, Australia; S X Dou; Sch. of Mater. Sci. & Eng., New South Wales Univ., Kensington, NSW, Australia; A J Bourdillon; Sch. of Mater. Sci. & Eng., New South Wales Univ., Kensington, NSW, Australia; C C Sorrell; Sch. of Mater. Sci. & Eng., New South Wales Univ., Kensington, NSW, Australia
Журнал:
Superconductor Science and Technology
Дата:
1988-12-01
Аннотация:
The chemical behaviour of both YBa<sub>2</sub>Cu<sub>3</sub>O<sub>6.5+y</sub> (123) and Bi<sub>2</sub>Sr<sub>2</sub>CaCu<sub>2</sub>O<sub>8+y</sub> (2212) in various solvents was studied in a comparative manner. In both compounds superconductivity apparently depends on a high-oxidation state of Cu. Electrochemical corrosion rates were measured by a variety of techniques and are related to the concentration of labile Cu<sup>3+</sup> ions in the specimens. Generally (2212) is the more stable compound, except in strongly basic solutions owing to the amphoteric nature of Bi. In the presence of acidic or basic solutions Bi<sup>3+</sup> is oxidised to Bi<sup>4+</sup> or Bi<sup>5+</sup> by the high-oxidation state of Cu in (2212) (similar to oxidation by Na<sub>2</sub>O<sub>2</sub>), demonstrating a common feature of cuprate superconductors. The concentration of labile ions was determined by the volumetric measurement of evolved oxygen from acid solution, and the technique was extended to measure the concentration of undecomposed or re-formed carbonates after sintering.
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