The Role Of Non Stoichiometry In The Functional Properties Of Oxide Materials

The interrelation among composition, microstructure, and properties of stoichiometric and nonstoichiometric compounds is a major field of research for both scientific and technological reasons. As such, this book focuses on metal oxides, which present a large diversity of electrical, magnetic, optical, optoelectronic, thermal, electrochemical, and catalytic properties, making them suitable for a wide range of applications. By bringing together scientific contributions with special emphasis on the interrelations between materials chemistry, processing, microstructures, and properties of stoichiometric and nonstoichiometric metal oxides, this book highlights the importance of tightly integrating high-throughput experiments (including both synthesis and characterization) and efficient and robust theory for the design of advanced materials.

Functional oxides have a wide variety of applications in the electronic industry. The discovery of new metal oxides with interesting and useful properties continues to drive much research in chemistry, physics, and materials science. In Functional Oxides five topical areas have been selected to illustrate the importance of metal oxides in modern materials chemistry: Noncentrosymmetric Inorganic Oxide Materials Geometrically Frustrated Magnetic Materials Lithium Ion Conduction in Oxides Thermoelectric Oxides Transition Metal Oxides - Magnetoresistance and Half-Metallicity The contents highlight structural chemistry, magnetic and electronic properties, ionic conduction and other emerging areas of importance, such as thermoelectricity and spintronics. Functional Oxides covers these complex concepts in a clear and accessible manner providing an excellent introduction to this broad subject area.

The material in this book is based on invited and contributed pa pers presented at the NATO Advanced Research Workshop on INon-stoichio l metric Compounds held in Ringberg Castle, Rottach-Egern (Bavarian Alps), Germany, July 3-9, 1988. The workshop followed previous meetings held in Mogilany, Poland (1980), Alenya, France (1982), Penn State, USA (1984) and Keele University, UK (1986). The aim of these workshops is to present and discuss up-to-date knowledge in the study of non-stoichiometry and its effect on materials properties as well as to indicate the most urgent research pathways required in this field. Since the subject of non-stoichiometry is interdisciplinary, the workshops bring together solid state physicists and chemists, surface scientists, materials scientists, ceramists and metallurgists. The present workshop, which gathered 42 scientists of an inter national reputation, mainly considered the effect of surfaces, grain boundaries and structural defects on materials properties. From discus sions during this meeting it emerged that correct understanding of properties of ceramic materials requires urgent studies on the defect structure of the interface region. Progress in this direction requires the development of the interface defect chemistry. This is the task for materials scientists in the near future. The present proceedings includes both theoretical and experimen tal work on general aspects of non-stoichiometry, defect structure and diffusion in relation to the bulk and to the interface region of such materials as high tech ceramics, solid electrolytes, electronic cera mics, nuclear materials and high Tc oxide superconductors.

Perovskite Metal Oxides: Synthesis, Properties and Applications provides an overview on the topic, including the synthesis of various types of perovskites, their properties, characterization and application. The book reviews the applications of this category of materials for photovoltaics, electronics, biomedical, fuel cell, photocatalyst, sensor, energy storage and catalysis, along with processing techniques of perovskite metal oxides with a focus on low-cost and high-efficiency methods, including various properties and probable applications in academia and industry. Other sections discuss strategies to improve the functionality of perovskite metal oxide materials, including chemical methods and controlling the size, shape and structure of the materials. Finally, applications of perovskite metal oxides in energy conversion and storage, sensing and electronics are covered. Provides an overview of perovskite metal oxides, with an emphasis on synthesis, fabrication and characterization methods Discusses strategies to improve the functionality of perovskite metal oxide materials, including chemical methods and controlling the size, shape and structure of the materials Reviews applications of perovskite metal oxides in energy conversion and storage, sensing and electronics

The Electrocaloric Effect: Materials and Applications reviews the fundamentals of the electrocaloric effect, the most relevant electrocaloric materials, and electrocaloric measurements and device applications. The book introduces the electrocaloric effect, along with modeling and simulations of this effect. Then, it addresses the latest advances in synthesis, characterization and optimization of the most relevant electrocaloric materials, including ferroelectric materials, liquid materials, lead-free materials, polymers and composites. Finally, there is a review of the latest techniques in measurement and applications in refrigeration and cooling and a discussion of the advantages, challenges and perspectives of the future of electrocaloric refrigeration. Provides a comprehensive introduction to the electrocaloric effect including experimental techniques to measure, model, and simulate the effect Reviews the most relevant electrocaloric materials such as composites, polymers, metal oxides, ferroelectric materials, and more Touches on the design and application of electrocaloric materials for devices with potential cooling and refrigeration applications

This book shows how a small toolbox of experimental techniques, physical chemistry concepts as well as quantum/classical mechanics and statistical methods can be used to understand, explain and even predict extraordinary applications of these advanced engineering materials and biomolecules. It highlights how improving the material foresight by design, including the fundamental understanding of their physical and chemical properties, can provide new technological levels in the future.

Electrochemical energy conversion and storage devices including solid oxide fuel cells (SOFCs) and lithium ion batteries (LIBs) are enabled by materials known as "non-stoichiometric oxides" that contain large concentrations of point defects such as oxygen or lithium vacancies. While this non-stoichiometry provides the essential functional properties of ionic conductivity or reactivity that make these materials useful, it also tends to couple to material volume through the effect of chemical expansion. Chemical expansion, or volume coupled to defect concentration, is in turn tied to mechanical variables including stress, strain, and elastic constants. This electrochemomechanical coupling, or interaction between functional properties, defect chemistry, and mechanical variables, can have important consequences for devices operated in extreme environments, where unexpected stress may lead to fracture, or well-engineered strain may enhance device efficiency. Such effects are particularly important in thin film devices, where strain engineering is within reach, undesired fracture can devastate performance, and defect chemistry and related properties can differ from bulk systems. In this thesis, we present a concerted investigation of chemomechanical coupling, including interactions between material chemistry, environmental conditions, stress, strain, and mechanical properties, for films of the model material PrxCe1-xO2-[delta] (PCO) that is a fluorite-structured oxide relevant to SOFC applications. PCO is an excellent model system because of its well-established defect chemistry model and known thermal and chemical expansion coefficients. The thesis begins by first characterizing key chemomechanical effects in PCO, including electrochemically induced high temperature actuation and nonstoichiometry- dependent mechanical properties that are modulated by environmental conditions including temperature and oxygen partial pressure. We then explore the mechanisms and microstructural contributions to these effects via computational modeling and high temperature transmission electron microscopy, identifying ways in which chemomechanical effects in thin film non-stoichiometric oxides differ from those in bulk. Finally, we extend the experimental and computational methods developed in the thesis to characterizing similar effects in Li-storage materials, demonstrating the broad applicability of results across the classes of non-stoichiometric oxides. We first describe an experimental study in which we developed a novel method of detecting chemical expansion on short time scales in the model system PCO and characterized material deformation for a range of conditions of temperature and effective oxygen partial pressure (pO2). In this method, electrically-stimulated chemical expansion caused mechanical deflection of a substrate, an effect that for PCO was enhanced for elevated temperatures or reducing conditions ...

This book summarizes the current knowledge of two-dimensional oxide materials. The fundamental properties of 2-D oxide systems are explored in terms of atomic structure, electronic behavior and surface chemistry. The concept of polarity in determining the stability of 2-D oxide layers is examined, charge transfer effects in ultrathin oxide films are reviewed as well as the role of defects in 2-D oxide films. The novel structure concepts that apply in oxide systems of low dimensionality are addressed, and a chapter giving an overview of state-of-the-art theoretical methods for electronic structure determination of nanostructured oxides is included. Special emphasis is given to a balanced view from the experimental and the theoretical side. Two-dimensional materials, and 2-D oxides in particular, have outstanding behavior due to dimensionality and proximity effects. Several chapters treat prototypical model systems as illustrative examples to discuss the peculiar physical and chemical properties of 2-D oxide systems. The chapters are written by renowned experts in the field.

As the finite capacity and pollution problems of fossil fuels grow more pressing, new sources of more sustainable energy are being developed. Materials for energy conversion devices summarises the key research on new materials which can be used to generate clean and renewable energy or to help manage problems from existing energy sources. The book discusses the range of materials that can be used to harness and convert solar energy in particular, including the properties of oxide materials and their use in producing hydrogen fuel. It covers thermoelectric materials and devices for power generation, ionic conductors and new types of fuel cell. There are also chapters on the use of such materials in the immobilisation of nuclear waste and as electrochemical gas sensors for emission control. With its distinguished editors and international team of contributors, Materials for energy conversion devices is a standard reference for all those researching and developing a new generation of materials and technologies for our energy need. Detailed coverage of solar energy and thermoelectric conversion Comprehensive survey of new developments in this exciting field Edited by leading experts in the field with contributions from an international team of authors