Springer Online Journal Archives 1860-2000
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Abstract The change in electrical resistance with time for bulk, thick-film, and thin-film Ba2YCu3Ox at atmospheric pressure is described as a function of the oxygen partial pressure (100 to 0.001%) and temperature (320°–750°C). The potential usefulness of these materials as oxygen sensors is demonstrated. The rate of equilibration is faster during oxygen uptake than during its loss. Time constants τ to reach equilibration (1/e remaining), qualitatively scale with sample dimensions. For a 1μm film at 600° C,τ 〈1 s for the range of PO2 (O2 being a shorthand for O2) from 100% to 0.001%. The rate increases markedly with increasing PO2. The actual resistance decreases with PO2 at a rate of logρ/log PO2 = 0.4 at 700° C showing adequate sensitivity for sensor purposes. Times for the transient resistance change in the sample where used to estimate the oxygen diffusion coefficient in the ceramic. The diffusivities obtained are 4·10−11−1·10−12 cm2/s in the 435°–320° C range, with an activation energy of ≅27 kcal/mole.
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