Low‐Temperature Superionic Conductivity in Strained Yttria‐Stabilized Zirconia

Abstract

AbstractVery 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.