Use of Stabilized ZrO2 to Measure O2 Permeation |
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Authors: | K. KITAZAWA R. L. COBLE |
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Affiliation: | Department of Metallurgy and Materials Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 |
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Abstract: | The rate of permeation of CaO-stabilized ZrO2 (CSZ) by O2 gas was measured from 640° to 1200°C with the CSZ tubing used simultaneously as the sample and the O2 pressure detector. The apparent permeation rate depended significantly on the O2 pressure at the low-pressure side. The rate measured by this method was orders of magnitude smaller than that measured under steady-state conditions, except when the O2 partial pressure was high (>10−4 atm), in which case the agreement was good. The difference between steady-state permeability and non-steady-state permeability is related to the deviation in stoichiometry in a sample or detector. The transient response (measured under variable pressure difference) may be very different from steady-state permeation (measured under constant differential pressures across the membranes). To apply CSZ to typical O2 gas permeability measurements, the O2 pressure must be kept above ∼ 10−3.5 atm. In this range, the permeability of CSZ may be regarded as a temperature-dependent material property which is governed by the electron-hole mobility. At lower O2 pressures the permeation rate is a more complex function of the pressure difference and level. |
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