Ionic Mobilities and Association Energies from an Analysis of Electrical Impedance of ZrO2–Y2O3 Alloys |
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Authors: | Jie Luo Darryl P Almond Ron Stevens |
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Affiliation: | Department of Materials Science and Engineering, University of Bath, Bath BA1 2XW, United Kingdom |
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Abstract: | The dc conductivities of ZrO2–Y2O3 ceramic alloys (in the range 3–12 mol% of Y2O3) have been obtained from ac impedance measurements at temperatures between 250° and 370°C. The Almond–West ac conductivity model has been applied to evaluate hopping rates in this system. The migration enthalpies were evaluated and shown to increase with yttria concentration, but all values determined were shown to be lower than the corresponding activation enthalpies for conductivity. The association enthalpies thus calculated were shown to be very small in 3 mol% Y2O3–ZrO3 and to increase with yttria concentration until the yttria contents were high enough to form fully stabilized cubic zirconia. For these samples the association enthalpies are about 0.19 eV, and no longer sensitive to yttria content. The low hopping rate at high yttria concentration might be attributed to low entropy in the system, which might be attributed to the formation of vacancy clusters and/or an ordering of the structure. |
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Keywords: | impedance zirconia yttria |
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