About this Research Topic
Functional oxide materials can show a plethora of emergent complex phenomena beyond their traditional role as dielectrics, including memristive effects, catalytic activity, energy conversion, and multiferroicity. Of further interest, nano-engineered oxides offer the possibility of realizing hitherto unobserved phenomena due to their unique responsiveness to external stimuli, multiple order-parameter couplings, and increased volume-to-surface ratio. Consequently, oxide-based materials are becoming increasingly more important for a variety of applications including transparent electronics, optoelectronics, magnetoelectronics, photonics, spintronics, thermoelectrics, piezoelectrics, power harvesting, hydrogen production and storage, and catalysis for energy and environmental concerns. And yet, controlled synthesis and thorough microscopic understanding of these materials remain a challenge.
Stoichiometry changes are ubiquitous in oxides and can considerably affect their structural, magnetic, chemisorption and catalytic, as well as transport properties. Non-stoichiometry is indeed a pivotal facet of the functioning of oxide materials. For instance, in transition metal oxide-based heterogeneous catalysis, the presence of oxygen vacancies is sometimes necessary for any activity. Oxygen vacancies can also significantly distort the equilibrium arrangement of atoms and modify the super-exchange interactions between neighboring magnetic ions, thus inducing spin-order transformations. Furthermore, extrinsic vacancies enable ionic conductivity in perovskite-based solid solutions to be used in electrochemical applications, such as solid oxide fuel and electrolytic cells. In addition, the defect dynamics are strongly influenced by local electric fields, domain boundaries, surface chemical potentials, and mechanical strain. Engineering of chemical defects in oxide compounds, therefore, emerges as a likely avenue for the design of new materials with tailored functionality. Likewise, an improved and more systematic understanding of how non-stoichiometry affects functionality will provide increasingly accurate ways of rationalizing the intriguing phenomena observed in oxide materials.
This Research Topic seeks to bring together experimental and theoretical researchers from diverse fields - such as information storage, catalysis, and energy conversion - to discuss the role of non-stoichiometry in the functional properties of oxide materials. Original research articles and reviews on the following topics (but not limited to these) are welcome:
- Synthesis and characterization of non-stoichiometric oxide ceramics and thin films
- Theory and simulation of crystalline defects in oxide materials
- Catalytic surfaces, nanostructures, and interfaces in oxides
- Ionic-conductor oxide materials
- Non-stoichiometric multiferroics and ferroelectrics
- Defect-induced magnetism in oxides
- Optical properties of non-stoichiometric oxides
- Electrochemical properties of non-stoichiometric oxide compounds
- Redox-stable and redox-active materials
- Chemically driven phase transitions in oxides
- Non-stoichiometric nuclear fuel oxides
- Sensors and actuators based on non-stoichiometric oxide materials
- Memristive switching oxide materials
Keywords: Catalysis, oxide-based materials, surfaces, theory and experiments, ionic defects
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