Impact of Oxygen Non‐Stoichiometry on Near‐Ambient Temperature Ionic Mobility in Polaronic Mixed‐Ionic‐Electronic Conducting Thin Films

Abstract

Enhanced ionic mobility in mixed ionic and electronic conducting solids contributes to improved performance of memristive memory, energy storage and conversion, and catalytic devices. Ionic mobility can be significantly depressed at reduced temperatures, for example, due to defect association and therefore needs to be monitored. Measurements of ionic transport in mixed conductors, however, proves to be difficult due to dominant electronic conductivity. This study examines the impact of different levels of quenched-in oxygen deficiency on the oxygen vacancy mobility near room temperature. A praseodymium doped ceria (Pr 0.1 Ce 0.9 O 2-δ) film is grown by pulsed laser deposition and annealed in various oxygen partial pressures to modify its oxygen vacancy concentration. Changes in film non-stoichiometry are monitored by tracking the optical absorption related to the oxidation state of Pr ions. A 13-fold increase in ionic mobility at 60 °C for increases in oxygen non-stoichiometry from 0.032 to 0.042 is detected with negligible changes in migration enthalpy and large changes in pre-factor. Several factors potentially contributing to the large pre-factor changes are examined and discussed. Insights into how ionic defect concentration can markedly impact ionic mobility should help in elucidating the origins of variations seen in nanoionic devices.

Engineering of Electromechanical Oxides by Symmetry Breaking

“…However, possible oxygen vacancy transport at or near room temperature raises open questions about the role of defect interactions and their mobility in highly defective configurations. [ 77 ] The low‐frequency electromechanical coupling could be associated with the range of charged defect motion and interfacial and chemical interactions. Thus, addressing these correlations and deriving correct electromechanical coefficients is important for understanding and manipulating the giant electromechanical coupling in doped ceria and similar fluorite systems.…”

Formation Energy Profiles of Oxygen Vacancies at Grain Boundaries in Perovskite‐Type Electroceramics

“…Especially oxygen vacancies, which can be present in the materials in large concentration ranges, enable many functionalities, such as electronic or ionic conductivity. [8,9] For the perovskite compound strontium titanate, SrTiO 3 (STO), the high diffusivity of oxygen vacancies allows the technologically promising effect of electric field-assisted sintering, specifically the growth of very large crystallites within the polycrystalline microstructure. [10] For an STO sample attached between oppositely charged electrodes in their experiment, Rheinheimer et al [10] stated a concentration gradient of oxygen vacancies.…”

“…Especially oxygen vacancies, which can be present in the materials in large concentration ranges, enable many functionalities, such as electronic or ionic conductivity. [ 8,9 ]…”