Lorenz, G.; Frey, Friedrich; Schulz, H.; Boysen, Hans
Structural investigations up to 1300 K and ionic conductivity in Ca-stabilized zirconia.
In: Solid State Ionics, Vol. 28-30, No. PART 1: pp. 497-502
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Cubic Ca-stabilized zirconia (CSZ) of composition Zr0.85Ca0.15O1.85 was investigated by neutron elastic Bragg scattering technique. Data were collected at 1170, 1370 and 1770 K and analysed in terms of split atom models and/or by an anharmonic temperature factor formalism for the oxygens. There are distinct deviations from the ideal fluorite structure at all the temperatures. At 1170 and 1370 K the derived split-atom positions along <100>, indicate a \"tetragonal\" distortion at least over a few cells. At 1770 K an analysis with anharmonic temperature factors and interstitital sites either along <xxx> or at <1/4 1/4 1/4> gives the best results. Significant nuclear scattering density is found away from the ideal <1/4 1/4 1/4> positions, which may be interpreted in terms of a mobile oxygen substructure. From the probability density function, Veff values are calculated, Low-lying barriers of 0.5-0.6 eV indicate the most probable diffusion pathways. In comparison with thermal energies these findings may be closely correlated with the enhanced ionic conductivity of CSZ observed at elevated temperatures.