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Electrochemical Probes of Oxidation State, Product Distribution, and Redox Activity for Ba sub 2 YCu sub 3 O sub (7-x) in Halide Solutions.

01 January 1989

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Measurements at a carbon or platinum ring electrode of a rotating Ba sub 2 YCu sub 3 O sub (7-x) disk - ring electrode configuration in acidified halide solutions allow several schemes for the real-time analysis of x. These methods, based on analyzing the flux of soluble material from the disk into chloride, bromide, and iodide solutions, can be applied over the range from semiconductor (O sub 6 - O sub (6.5)) to superconductive phases (O sub (6.5) O sub 7). Since the analytical methods depend either on measuring Cu sup (+2) / Cu sup (+1) ratios (for semiconductor phases) or the ratios ( for superconducting phases) of oxidized products to copper species (Br sub 2 to Cu sup (+2), I sub 3 sup - to CuI sub 2 sup -, in the respective halides), they are independent of such factors as sample size and dissolution rate, as long as the latter process is non-selective. Results for O sub 7 and O sub (6.2) content specimens have been confirmed against standard procedures. No Cu sup (+3) or readily reducible species surviving beyond the tens of millisecond transit time from the disk to ring are detectable in the chloride experiments. Model experiments with CuO and Cu sub 2 O disks established the identification of species and the quantitative basis of the methods.