Nanocrystalline (nc) scandia-stabilized zirconia (SSZ) electrolytes with scandia contents of 5.9 to 15.9 mol% ere synthesized by reactive magnetron sputtering. For scandia content >= 9.1 mol%, the as-deposited films were pure cubic phase with < 111 > texture, while traces of tetragonal phase was found for lower Sc content. Single-line profile analysis of the 111 X-ray diffraction peak yielded an out-of-plane grain size of similar to 10 nm and a microstrain of 2.0-2.2%, regardless of scandia content, for films deposited at 400 degrees C and a bias of -70 V. Films deposited at higher bias voltages showed a reduced grain size, yielding a grain size of similar to 6 nm and a microstrain of similar to 2.5% at -200 V and -250 V with additional incorporation of argon. Temperature-dependent impedance spectroscopy of the SSZ films showed that the in-plane ionic conductivity had a maximum close to 10.7 mol% and decreased almost an order of magnitude as the scandia - content was increased to 15.9 mol%. The activation energy for oxygen ion migration was determined to be between 130-1.43 eV. In addition, no dependence on grain size was observed. The above observations suggest a bulk mechanism for ionic conduction. (C) 2010 Elsevier B.V. All rights reserved.