Low-Temperature Superionic Conductivity in Strained Yttria-Stabilized Zirconia

• Published in: Advanced functional materials Vol. 20; no. 13; pp. 2071 - 2076
• Main Authors: Sillassen, Michael, Eklund, Per, Pryds, Nini, Johnson, Erik, Helmersson, Ulf, Bøttiger, Jørgen
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 09.07.2010; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Conductivity; Direct current; Dislocation density; electrolytes; epitaxy; Grain boundaries; interfaces; Ion currents; Ions; Low temperature; Magnesium oxide; Magnetron sputtering; Materials science; Misfit dislocations; sputtering; Strain; Substrates; TECHNOLOGY; TEKNIKVETENSKAP; Temperature; Thick films; Yttria-stabilized zirconia; Yttrium oxide; Zirconium dioxide
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201000071

Very high lateral ionic conductivities in epitaxial cubic yttria‐stabilized zirconia (YSZ) synthesized on single‐crystal SrTiO3 and MgO substrates by reactive direct current magnetron sputtering are reported. Superionic conductivities (i.e., ionic conductivities of the order ∼1 Ω−1cm−1) are observed at 500 °C for 58‐nm‐thick films on MgO. The results indicate a superposition of two parallel contributions – one due to bulk conductivity and one attributable to conduction along the film–substrate interface. Interfacial effects dominate the conductivity at low temperatures (<350 °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 °C are of great fundamental importance but may also be technologically relevant for low‐temperature applications. High lateral ionic conductivity enhancements are demonstrated at low temperatures in a simple model system consisting of single epitaxial YSZ layers synthesized on SrTiO3 and MgO single crystals, as compared to conventional bulk YSZ ceramics. The source of the enhancement is found at the interfaces due to the combined effect of strain and misfit dislocations.