Diffusion and ionic conductivity in sodium beta alumina |
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Authors: | KK Kim JN Mundy WK Chen |
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Institution: | Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, U.S.A. |
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Abstract: | Measurements of sodium tracer diffusion (Dt) and ionic conductivity (σ) have been made on the same single crystals of sodium beta-alumina of composition 1.23 Na20.11 Al2O3. The σ- measurements were made over the temperature 390–660 K using reversible (liquid sodium) electrodes. A fit to the conductivity data gives . The Dt, measurements employed two techniques, i.e. nondestructive profiling over the temperature range 210–750 K and cation exchange over the temperature range 505–970 K. The results of the two techniques were in close agreement and can be expressed as for T>520K and . The “transition” region between 470 and 520 K is not observed in the conductivity measurements. Silver cation exchange was used to determine the number of mobile sodium ions. A comparison of Dt and σ data yielded a Haven ratio that is temperature dependent, ranging in value from 0.45 at 870 K to 0.35 at 370 K. |
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