The B-site substituted perovskite oxides A(2)B'B '' O-6 have in the recent decades gained an increasing amount of interest due to their various interesting properties and possible applications. Here we survey the literature for ca. one thousand A(2)B'B '' O-6 perovskite compounds. Crystal structures and the various crystal chemistry features such as ordering and valence mixing of the B cations characteristic to these compounds are reviewed, together with their electronic and magnetic properties. Most importantly, the thorough examination of the research so far carried out allows us to make predictions for a number of new A(2)B'B '' O-6 compounds yet to be synthesized and reveal exciting but not yet fully explored puzzles related to this family of functional oxide materials. (C) 2014 Elsevier Ltd. All rights reserved.
Heusler compounds are a remarkable class of intermetallic materials with 1:1:1 (often called Half-Heusler) or 2:1:1 composition comprising more than 1500 members. Today, more than a century after their discovery by Fritz Heusler, they are still a field of active research. New properties and potential fields of applications emerge constantly: the prediction of topological insulators is the most recent example. Surprisingly, the properties of many Heusler compounds can easily be predicted by the valence electron count. Their extremely flexible electronic structure offers a toolbox which allows the realization of demanded but apparently contradictory functionalities within one ternary compound. Devices based on multifunctional properties, i.e. the combination of two or more functions such as superconductivity and topological edge states will revolutionize technological applications. The subgroup of more than 250 semiconductors is of high relevance for the development of novel materials for energy technologies. Their band gaps can readily be tuned from zero to approximate to 4 eV by changing the chemical composition. Thus, great interest has been attracted in the fields of thermoelectrics and solar cell research. The wide range of their multifunctional properties is also reflected in extraordinary magneto-optical, magnetoelectronic, and magnetocaloric properties. The most prominent example is the combination of magnetism and exceptional transport properties in spintronic devices. To take advantage of the extremely high potential of Heusler compounds simple rules for the understanding of the structure, the electronic structure and the relation to the properties are reviewed. (C) 2011 Elsevier Ltd. All rights reserved.
Transparent polycrystalline ceramics have found various applications, such as laser hosts, infrared (IR) windows/domes, lamp envelopes and transparent armors, instead of their single crystal counterparts, due mainly to their processing flexibility in fabricating items with large sizes and complex shapes and more importantly cost-effectiveness. High optical transparent ceramics require high purity and high density. To achieve high purity final products, it is necessary to use high purity precursor powders. To get high density, various sintering technologies have been employed, such as high-pressure (HP) sintering, high isostatic pressure (HIP) sintering, vacuum sintering and spark plasma sintering (SPS). At the same time, various wet chemical synthesis routes have been used to produce precursor powders at submicron or even nanometer scales, with significantly improved sinterability. Transparent ceramics for armor and IR window/dome applications should have superior mechanical and thermal properties. Therefore, nanosized ceramics and nanocomposite ceramics have attracted much attention more recently. This review was aimed to summarize the latest progress in processing, materials and applications of transparent ceramics. It is arranged by starting with a brief introduction, followed by a detailed description on various sintering technologies used to develop transparent ceramics. After that, potential applications of transparent ceramics, together with their optical, mechanical and thermal properties, will be discussed. It will be concluded with discussions on future trend and perspectives, as well as some important issues, of transparent ceramic materials. (C) 2012 Elsevier Ltd. All rights reserved.
In this paper, the experimental and theoretical results that may give an insight into the current status and possible prospects of the family of (sp(1) + sp(2)) hybridized carbon allotropes: graphynes (GYs) and graphdiynes (GDYs), are reviewed. These allotropes, which can form a rich variety of 0D-3D forms and demonstrate a set of distinguished properties, have attracted now increased attention and research interest as promising materials, which can compete in various potential applications with "conventional" sp(2) carbon systems such as fullerenes, nanotubes or graphene and meet the increasing requirements to carbon-based nanomaterials. It can be seen from the increasing number of publications in the last five years that the interest in GYs and GDYs rapidly grows, and a lot of new results have been obtained today. For example, a set of 0D-3D forms of GYs and GDYs have been successfully synthesized and (or) predicted theoretically, and their key properties (structural, mechanical, electronic etc.) have been measured or estimated from ab initio calculations. This gives a strong impetus to further progress in applications of GYs and GDYs as materials for nanoelectronics, energy storage, as anode materials in batteries, as membranes for facilitating selective gas separation etc. All these efforts promote the expansion of the palette of promising carbon materials and accelerate the development of modern carbon-based technologies. (C) 2012 Elsevier Ltd. All rights reserved.
Electrolyte solutions have vital function in lithium-ion batteries. Due to their modular composition, there is a broad variety of electrolyte component combinations. In this work, we present electrochemical results on newly investigated electrolyte solution components. The standard electrolyte salt in commercial batteries, LIPF6, was replaced by new imide and sulfonate anion based salts, with enhanced stability. The use of propylene carbonate was enabled by the application of new SEI forming electrolyte additives. Electrolyte solvents, such as adiponitrile and gamma-butyrolactone were investigated in combination with LiBF4 as electrolyte salt. In order to evaluate these materials, various electrochemical techniques like galvanostatic cycling, conductivity and electrochemical stability window detection, cyclic voltammetry, etc. were applied. Furthermore, the electrode/electrolyte interfaces and interphases were studied via spectroscopic and spectrometric techniques. (C) 2014 Elsevier Ltd. All rights reserved.
This report deals with the mechanism behind the unusual behavior of nanostructures in mechanical strength, thermal stability, acoustics (lattice dynamics), photonics, electronics, magnetism, dielectrics, and chemical reactivity and its indication for designing and fabricating nanostructured materials with desired functions. A bond-order-length-strength (BOLS) correlation mechanism has been initiated and intensively verified, which has enabled the tunability of a variety of properties of a nanosolid to be universally reconciled to the effect of bond order deficiency of atoms at sites surrounding defects or near the surface edges of the nanosolid. The BOLS correlation indicates that atomic coordination imperfection causes the remaining bonds of the under-coordinated atom to contract spontaneously associated with bond strength gain and the intraatomic trapping potential well depression. Consequently, localized densification of charge, energy and mass occurs to the surface skin, which modify the atomic coherency (the product of bond number and the single bond energy), electroaffinity (separation between the vacuum level and the conduction band edge), work function, and the Hamiltonian of the nanosolid. Therefore, any detectable quantity can be functionalized depending on the atomic coherency, electroaffinity, work function, Hamiltonian or their combinations. For instances, the perturbed Hamiltonian determines the entire band structure such as the band-gap expansion, core-level shift, Stokes shift (electron-phonon interaction), and dielectric suppression (electron polarization); The modified atomic coherency dictates the thermodynamic process of the solid such as self-assembly growth, atomic vibration, phase transition, diffusitivity, sinterbility, chemical reactivity, and thermal stability. The joint effect of atomic coherency and energy density dictates the mechanical strength (surface stress, surface energy, Young's modulus), and compressibility (extensibility, or ductility) of a nanosolid. Most strikingly, a combination of the new freedom of size and the original BOLS correlation has allowed us to gain quantitative information about the single energy levels of an isolated atom and the vibration frequency of an isolated dimer, and the bonding identities in the metallic monatomic chains and in the carbon nanotubes. A survey and analysis of the theoretical and experimental observations available to date demonstrated that the under-coordinated atoms in the surface skin of 2-3 atomic layers dictate the performance of nanostructures yet atoms of the interior remain as they are in the bulk counterpart. Further extension of the BOLS correlation and the associated approaches to atomic defects, impurities, liquid surfaces, junction interfaces, and amorphous states and to the temperature domain would be more challenging, fascinating, and rewarding. (C) 2006 Elsevier Ltd. All rights reserved.
An extensive and wide-ranging literature about the polymorphs of titanium dioxide (TiO2) has accumulated during the last few decades, providing a very large resource of data on its properties, functionality and many present and potential industrial uses. This review focuses on the structural, kinetic, thermodynamic and electrical properties of TiO2 from the viewpoint of the relationship between the crystal structure and its present or potential useful functionality, via the electronic structure. The reason for this focus is the fundamental relationship between the electronic band structure of this wide band gap semiconductor and its interaction with light and chemical species. Intense interest in the photo activity of TiO2 followed the demonstration by Fujishima and Honda in 1972 of its ability to dissociate water using sunlight Approaches to band gap engineering via chemical modifications are surveyed and correlated with band-structure calculations using Density Functional Theory and Hartree Fock methods. In the last section, progress in TiO2 applications and prospects for new applications of this material are summarised. (C) 2016 Elsevier Ltd. All rights reserved.
The utilization of solar irradiation to supply energy or to initiate chemical reactions is already an established idea. If a wide-band gap semiconductor like titanium dioxide (TiO2) is irradiated with light, excited electron-hole pairs result that can be applied in solar cells to generate electricity or in chemical processes to create or degrade specific compounds. Recently, a new process used on the surface of TiO2 films, namely, photoinduced super-hydrophilicity, is described. All three appearances of the photoreactivity of TiO2 are discussed in detail in this review, but the main focus is on the photocatalytic activity towards environmentally hazardous compounds (organic, inorganic, and biological materials), which are found in wastewater or in air. Besides information on the mechanistical aspects and applications of these kinds of reactions, a description of the attempts and possibilities to improve the reactivity is also provided. This paper would like to assist the reader in getting an overview of this exciting, but also complicated, field. (C) 2004 Elsevier Ltd. All rights reserved.
Since the first investigations of perovskite type oxynitrides with the generalised composition ABO(3-x)N(x) about twenty years ago, these compounds have become of growing interest. The incorporation of nitride ions in the perovskite lattice results in distinct changes in the electronic structure leading to unusual physical properties. In this article we report on new synthesis techniques, different analytical methods, progress in the structural characterisation by comprehensive diffraction techniques and local spectroscopic methods like XAS and NMR as well as state of the art theoretical investigations. Various physical characteristics like electrical and thermal transport parameters and dielectric properties are described. The thermal and chemical stability of oxynitride perovskites are investigated and their applications in different photocatalytic reactions are discussed. (C) 2009 Elsevier Ltd. All rights reserved.
Magnetic nanoparticles have attracted attention because of their Current and potential usefulness as contrast agents for magnetic resonance imaging (MRI) or colloidal mediators for cancer magnetic hyperthermia. This contribution examines these in vivo applications through an understanding of the involved problems and the Current and future possibilities for resolving them. A special emphasis is made on magnetic nanoparticle requirements from a physical viewpoint (e.g. relaxivity for MRI and specific absorption rate for hyperthermia). the factors affecting their biodistribution and the solutions envisaged for enhancing their half-life in the blood compartment and targeting tumour cells. Then. the synthesis strategies developed in our group are presented and focused on covalent platforms capable to be tailor-derivatised by surface molecular chemistry. The opportunity of using more complex oxides than conventional magnetite for controlling the in vivo temperature is also discussed. (C) 2005 Elsevier Ltd. All rights reserved.
The perovskite structure is one of the most wonderful to exist in nature. It obeys to a quite simple chemical formula, ABX(3), in which A and B are metallic cations and X, an anion, usually oxygen. The anion packing is rather compact and leaves interstices for large A and small B cations. The A cation can be mono, di or trivalent, whereas B can be a di, tri, tetra, penta or hexavalent cation. This gives an extraordinary possibility of different combinations and partial or total substitutions, resulting in an incredible large number of compounds. Their physical and chemical properties strongly depend on the nature and oxidation states of cations, on the anionic and cationic stoichiometry, on the crystalline structure and elaboration techniques, etc. In this work, we review the different and most usual crystalline representations of perovskites, from high (cubic) to low (triclinic) symmetries, some well-known preparation methods, insisting for instance, in quite novel and original techniques such as the mechanosynthesis processing. Physical properties are reviewed, emphasizing the electrical (proton, ionic or mixed conductors) and catalytic properties of Mn- and Co-based perovskites; a thorough view on the ferroelectric properties is presented, including piezoelectricity, thermistors or pyroelectric characteristics, just to mention some of them; relaxors, microwave and optical features are also discussed, to end up with magnetism, superconductivity and multiferroIsme. Some materials discussed herein have already accomplished their way but others have promising horizons in both fundamental and applied research. To our knowledge, no much work exists to relate the crystalline nature of the different perovskite-type compounds with their properties and synthesis procedures, in particular with the most recent and newest processes such as the mechanosynthesis approach. Although this is not intended to be a full review of all existing perovskite materials, this report offers a good compilation of the main compounds, their structure and microstructure, processing and relationships between these features. (C) 2015 Elsevier Ltd. All rights reserved.
Calcium phosphates with clinical applications are used in reconstructive surgery. When dealing with the repairing of a skeletal section, two extremely diverse routes could be initially considered: to replace the damaged part or to Substitute it regenerating the bone. This second option is in fact the role played by calcium phosphates, which call be classified among the bioactive ceramics group. Bioceramics, and therefore, calcium phosphates, exhibit very good biocompatibility and bone integration qualities, and constitute the materials showing closest similarity to the mineral component of bone; this fact, together with their bioactivity. make them very good candidates for bone regeneration. This review is focused on calcium phosphate ceramics; therefore, it is important to analyse firstly the biological calcium phosphates as components of natural hard tissues, that is, bone and teeth. and then to look for synthetic methods able to produce calcium deficient carbonate apatites with nanometric size, i.e., showing similar features to the biological apatites. In the present work, we describe the synthesis procedures to obtain in tile laboratory calcium deficient carbonate nanoapatite both in bulk and thin film forms, as well as the characterization methods applied to these materials, with particular incidence in the electron microscopy. (C) 2004 Elsevier Ltd. All rights reserved.
Si,Al containing nitride and oxynitride phosphors have been applied to white LEDs. Phosphors play important roles to produce high color rendering in lighting and wide color gamut in display. Si,Al containing nitrides and oxynitrides have been studied as high-temperature materials with high strength and thermal shock resistance. The inherited high temperature property is utilized as low thermal quenching in luminescence. The increased covalent bonding character compared to oxide phosphors contributes to high efficiency in blue excitation. The crystal structure (especially the coordination sphere around luminescent center) dominates the luminescent property of phosphor. Wide variety of crystal structure in Si,Al containing nitride and oxynitride leads to multiplicity of luminescent property. In this contribution, SLAI containing nitride and oxynitride phosphors are reviewed from viewpoints of synthesis, new phosphor discovery, and crystal structure.
Since the discovery of carbon nanotubes, there has been great interest in the synthesis and characterization of other one-dimensional materials. A variety of inorganic materials have been prepared in the form of nanowires with a diameter of a few nm and lengths going up to several microns. In order to produce the nanowires, both vapor-growth and solution-growth processes have been made use of. Besides physical methods, such as thermal evaporation and laser ablation, chemical methods including solvothermal, hydrothermal and carbothermal reactions have been employed for their synthesis. In this article, we describe the synthesis, structure and properties of nanowires of various inorganic materials, which include elements, oxides, nitrides, carbides and chalcogenides. Wherever possible, we have also included the relevant information on related one-dimensional materials, such as nanobelts. (C) 2003 Elsevier Ltd. All rights reserved.
This review covers various aspects of electrolyte investigations. The first section reports on synthesis and characterization of lithium salts and ionic liquids, including some unpublished recent work. The next part is devoted to transference number measurements of lithium ions. It contains recently published work and new results on this rarely investigated but important topic. Studies of anodic aluminum dissolution with our novel fast impedance scanning electrochemical quartz microbalance (FIS-EQCM) follow next. After a short introduction to the method, some recently published results are reviewed along with some yet unpublished material. We have also shown that the solubility of solids and gases in liquids can be measured with this equipment, including the solubility of lithium salts in ionic liquids. First results of FIS-EQCM studies show that electroplating and corrosion of lithium and subsequent dissolution of the SEI can be studied as well. The last parts of this manuscript are dedicated to the investigation of miscellaneous topics that are of interest for studies of electrolytes for LIBs. (C) 2014 Elsevier Ltd. All rights reserved.
Chalcogenide glasses (ChG) has emerged as important materials due to their potential applications in infrared optics for communication, imaging, limiting, remote sensing and laser power delivery etc. Examining ChG for their various applications, different properties of these were under immense investigation by various researchers from nearly every part of the world. Study of ChG for optical properties like optical band gap and refractive index are the backbone while considering them for applications. The present review focuses on the optical properties of various binary, ternary and quaternary chalcogenide systems. Subsequently applications and future prospects of ChG have been sketched. The attracting prospective applications have drive us to put the review on optical properties of chalcogenide thin films both comprehensive and expedient to new as well as established researchers in this area. (C) 2016 Elsevier Ltd. All rights reserved.
Reduction of CO2 using a heterogeneous photocatalyst under visible light has been studied as a potential means to address the problems of global warming and the depletion of fossil fuels. Recently, hybrid photocatalysts constructed with a metal complex and a particulate semiconductor are of particular interest because of the excellent electrochemical (and/or photocatalytic) ability of the metal complexes for CO2 reduction and the high efficiency of the semiconductors for oxidation reactions, where the ultimate target of oxidation reaction is water oxidation to form molecular O-2. This review article highlights our recent progress in the development of metalcomplex/semiconductor hybrid materials for visible-light CO2 reduction with a focus on oxynitride and nitride materials as the semiconductor component.
Materials that combine ferroic properties, such as ferromagnetism and ferroelectricity are highly desirable, yet rare. The number of candidate materials is limited and their effects are typically too small at room temperature to be useful in applications. Bismuth ferrite (BiFeO3) is potentially the only material which is both magnetic and highly ferroelectric at room temperature. Nanostructured BiFeO3 are promising materials for magnetoelectric and spintronic devices, especially the memories that can be addressed both electrically and magnetically. This review paper investigates the structural, microstructural, physical concepts and different synthesis methods of BiFeO3. (C) 2012 Elsevier Ltd. All rights reserved.