Low‐Temperature Superionic Conductivity in Strained Yttria‐Stabilized Zirconia

Abstract

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.

Tensile Lattice Distortion Does Not Affect Oxygen Transport in Yttria-Stabilized Zirconia–CeO2 Heterointerfaces

“…In general, literature data are quite consistent concerning the increased oxygen-ion conductivity of interfaces showing a large dislocation density, 4,7,9 but whether the interfacial strain can play a significant role in enhancing the ionic conductivity is still quite a controversial issue.…”

“…6,9 However, STO is not a good insulator at high temperatures, and conductivity measurements of thin films deposited on STO might be significantly affected by the substrate. 11 (100) and (110) MgO substrates, for which the insulating properties at high temperatures are well demonstrated, have been used for the fabrication of grain-boundary-free ultra-thin 8.7 mol% yttriastabilized zirconia (8.7YSZ 1 ) layers.…”

Strontium Diffusion in Magnetron Sputtered Gadolinia‐Doped Ceria Thin Film Barrier Coatings for Solid Oxide Fuel Cells

“…[5][6][7][8][9] Looking at the SOFC system perspective it is insufficient only to improve a single cell component in order to drastically increase the cell performance as it has been shown that all cell components (cathode, electrolyte, and anode) contribute with considerable losses in the SOFC. [10] Therefore, work on novel cathode materials is highly important.…”

Edge dislocation slows down oxide ion diffusion in doped CeO2 by segregation of charged defects

“…Because of what is known in metals, dislocations have been therefore suggested to enhance ionic conductivity in oxides as well [28][29][30] . For example, Sillassen et al 28 have observed 3.5 orders of magnitude acceleration in the ionic conductivity for a 8.7 mol.% yttria-stabilized zirconia (YSZ) epitaxial film on MgO substrate. They attributed this enhancement qualitatively to a combination of misfit dislocations and elastic strain at the interface.…”