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We report very high lateral ionic conductivities in epitaxial cubic yttria-stabilized zirconia synthesized on single crystal SrTiO 3 and MgO substrates by reactive direct current magnetron sputtering. Superionic conductivities (i.e., ionic conductivities of the order ~1 Ω -1 cm -1 ) are observed at 500 ºC for 58-nm-thick films on MgO. Our results indicate a superposition of two parallel contributions -one due to bulk and one attributable to the film-substrate interface.Interfacial effects dominate the conductivity at low temperatures (<350 o C), showing more than three orders of magnitude enhancement compared to bulk YSZ. At higher temperatures, a more bulk-like conductivity is observed. The films have a negligible grain-boundary network, thus ruling out grain boundaries as a pathway for ionic conduction. The observed enhancement in lateral ionic conductivity is caused by a combination of misfit dislocation density and elastic strain in the interface. These very high ionic conductivities in the temperature range 150 -500 ºC are of great fundamental importance but may also be technologically relevant for low-temperature applications.

Sillassen, M.; Eklund, P.; Sridharan, M.; Pryds, Nini; Bonanos, Nikolaos; Bøttiger, J. Published in: Journal of Applied PhysicsLink to article, DOI: 10.1063/1.3130404 Publication date: 2009 Document VersionPublisher's PDF, also known as Version of record Link back to DTU Orbit Citation (APA): Sillassen, M., Eklund, P., Sridharan, M., Pryds, N., Bonanos, N., & Bøttiger, J. (2009 Thermally stable, stoichiometric, cubic yttria-stabilized zirconia ͑YSZ͒ thin-film electrolytes have been synthesized by reactive pulsed dc magnetron sputtering from a Zr-Y ͑80/ 20 at. %͒ alloy target. Films deposited at floating potential had a ͗111͘ texture. Single-line profile analysis of the 111 x-ray diffraction peak yielded a grain size of ϳ20 nm and a microstrain of ϳ2% regardless of deposition temperature. Films deposited at 400°C and selected bias voltages in the range from Ϫ70 to Ϫ200 V showed a reduced grain size for higher bias voltages, yielding a grain size of ϳ6 nm and a microstrain of ϳ2.5% at bias voltages of Ϫ175 and Ϫ200 V with additional incorporation of argon. The films were thermally stable; very limited grain coarsening was observed up to an annealing temperature of 800°C. Temperature-dependent impedance spectroscopy analysis of the YSZ films with Ag electrodes showed that the in-plane ionic conductivity was within one order of magnitude higher in films deposited with substrate bias corresponding to a decrease in grain size compared to films deposited at floating potential. This suggests that there is a significant contribution to the ionic conductivity from grain boundaries. The activation energy for oxygen ion migration was determined to be between 1.14 and 1.30 eV.

Zinc antimonide thin films with high thermoelectric performance are produced by a simple sputtering method. The phase-pure Zn(4)Sb(3) and ZnSb thin films fulfill the key requirements for commercial TE power generation: cheap elements, cheap fabrication method, high performance and thermal stability. In addition, two completely new meta-stable crystalline phases of zinc antimonide have been discovered.