In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Progress in preparation, processing and applications of polyaniline

2.1.2. Low Topology/Framework Density 1003 2.1.3. Side Group Directed Superstructures 1003 2.2. Synthesis Considerations 1003 2.3. Special Properties 1004 3. Metal Imidazolate Frameworks 1004 3.1. Chains and Rings 1004 3.2. Zeolitic and Zeolite-like Frameworks 1006 3.2.1. SOD-Type Zinc(II) 2-Methylimidazolate 1007 3.3. Nonporous 4-Connected Networks 1010 3.4. Polyimidazolates 1011 4. Metal Pyrazolate Frameworks 1011 4.1. Clusters and Chains 1011 4.2. 3D Networks Based on Polypyrazolates 1012 5. Metal 1,2,4-Triazolate Frameworks 1014 5.1. Simple 3-Connected Networks 1015 5.2. Quasi-Imidazolates 1018 5.3. With Coordinative Substituents 1019 5.4. With Secondary Counterions and/or Ligands 1021 6. Metal 1,2,3-Triazolate Frameworks 1023 7. Metal Tetrazolate Frameworks 1025 7.1. Univalent Coinage-Metal Tetrazolate Frameworks 1025

Metal Azolate Frameworks: From Crystal Engineering to Functional Materials

Platinum-based nanostructured materials: synthesis, properties, and applications.

Electrochromic (EC) materials are able to change their optical properties, reversibly and persistently, by the application of an electrical voltage. These materials can be integrated in multilayer devices capable of modulating the optical transmittance between widely separated extrema. We first review the recent literature on inorganic EC materials and point out that today's research is focused on tungsten oxide (colouring under charge insertion) and nickel oxide (colouring under charge extraction). The properties of thin films of these materials are then discussed in detail with foci on recent results from two comprehensive investigations in the authors' laboratory. A logical exposition is obtained by covering, in sequence, structural features, thin film deposition (by sputtering), electronic band structure, and ion diffusion. A novel conceptual model is given for structural characteristics of amorphous W oxide films, based on notions of defects in the ideal amorphous state. It is also shown that the conduction band density of states is obtainable from simple electrochemical chronopotentiometry. Ion intercalation causes the charge-compensating electrons to enter localized states, implying that the optical absorption underlying the electrochromism can be described as ensuing from transitions between occupied and empty localized conduction band states. A fully quantitative theory of such transitions is not available, but the optical absorption can be modeled more phenomenologically as due to a superposition of transitions between different charge states of the W ions (6+, 5+, and 4+). The Ni oxide films were found to have a porous structure comprised of small grains. The data are consistent with EC coloration being a surface phenomenon, most likely confined to the outer parts of the grains. Initial electrochemical cycling was found to transform hydrated Ni oxide into hydroxide and oxy-hydroxide phases on the grain surfaces. Electrochromism in thus stabilized films is consistent with reversible changes between Ni hydroxide and oxy-hydroxide, in accordance with the Bode reaction scheme. An extension of this model is put forward to account for changes of NiO to Ni2O3. It was demonstrated that electrochromism is associated solely with proton transfer. Data on chemical diffusion coefficients are interpreted for polycrystalline W oxide and Ni oxide in terms of the lattice gas model with interaction. The later part of this review is of a more technological and applications oriented character and is based on the fact that EC devices with large optical modulation can be accomplished essentially by connecting W-oxide-based and Ni-oxide-based films through a layer serving as a pure ion conductor. Specifically, we treat methods to enhance the bleached-state transmittance by mixing the Ni oxide with other oxides characterized by wide band gaps, and we also discuss pre-assembly charge insertion and extraction by facile gas treatments of the films, as well as practical device manufacturing and device testing. Here the emphasis is on novel flexible polyester-foil-based devices. The final part deals with applications with emphasis on architectural “smart” windows capable of achieving improved indoor comfort jointly with significant energy savings due to lowered demands for space cooling. Eyewear applications are touched upon as well.

/pdf/electrochromics-for-smart-windows-thin-films-of-tungsten-aw0rai8h60.pdf

Electrochromics for smart windows: thin films of tungsten oxide and nickel oxide, and devices based on these

Comparative study of polyaniline cast films prepared from enzymatically and chemically synthesized polyaniline

XPS, AES, and EELS characterization of nitrogen-containing thin films

http://optica.machorro.net/Personal/Roberto/Arts/37_DiamRelMat03.pdf

Optical and surface analysis of DC-reactive sputtered AlN films

Au-zeolites with SiO2/Al2O3 molar ratios 10 and 206 were prepared by ion exchange of the H-mordenites with [Au(NH3)4](NO3)3 complex solution followed by hydrogen reduction or calcination at different temperatures. The samples were characterized by UV–visible DRS, XPS, XRD, TEM and TPR in order to understand the effect of zeolite acidity and pretreatment conditions on formation of different gold states. Three kinds of gold species were observed in the samples: (1) Au3+cations, (2) partly reduced species with the diameter less than 1 nm assigned to charged clusters Au n δ + (with n proposed ⩽8), suggested to be stabilized inside zeolite channels, and (3) Au0 nanoparticles with diameter varied within interval of 1.5–20 nm. The third type is located on the external surface of zeolite microcrystals. Au n δ + clusters were observed in as-prepared samples just after ion-exchange. Acid site strength did not change significantly amount of the clusters but influenced the electronic state of gold in these clusters and redox properties of gold cations. The contribution of the clusters was not changed significantly with temperature treatment even up to 500 °C. Au0 nanoparticles were formed by reduction of gold ions at temperatures starting from 50 to 200 °C depending on the medium of treatment and the molar ratio of the zeolite. The obtained results are important for understanding the effect of multiplicity of catalytically active gold species in CO oxidation.

Mario H. Farías

Papers

Comparative study of polyaniline cast films prepared from enzymatically and chemically synthesized polyaniline

XPS, AES, and EELS characterization of nitrogen-containing thin films

Optical and surface analysis of DC-reactive sputtered AlN films

Structure and electronic states of gold species in mordenites

Enzymatic synthesis of colloidal polyaniline particles