Electrical properties of a highly oriented, textured thin film of the ionic conductor Gd:CeO2-δ on (001) MgO

Highly oriented ionic conductor gadolinium-doped CeO2-delta (Ce0.8Gd0.2O2-delta) thin films have been grown on single-crystal (001) MgO substrates by pulsed-laser ablation. The films are highly c-axis oriented with cube-on-cube epitaxy, as shown by x-ray diffraction and electron microscopy. The interface relationship is, surprisingly, found to be (001)(film)//(001)(sub) and [100](film)//[100](sub) with an extremely large lattice misfit of more than 28%. Ac impedance measurements in the temperature range of 500 to 800 degreesC reveal that electrical conductivity is predominantly ionic over a very broad oxygen partial pressure range from pO(2) from 1x10(-19) atm to 1 atm. The activation energy E-a for ionic conductivity measured on unannealed films is 0.86 eV, but after heat treatment, E-a decreases to 0.74 eV. (C) 2003 American Institute of Physics.