Solid-state synthesis techniques

The ferroelectric Pb(Mgy3Nb2/3)03 (PMN) ceramic has been the snbject of extensive investigations due to its high dielectric coefficient and high electrostrictive coefficient, which renders it suitable for use in capacitors and electrostrictive actuators. However, the successful exploitation of this material is limited by the difficulty of producing a single-phase material with the perovskite structnre. Conventional solid state synthesis techniques invariably resnlt in the formation of one or more pyrochlore phases, which exhibit poor dielectric properties. 

At temperatures of 1100 C, it is evident that other phases have developed, but due to poor resolution of the x-ray data of the crushed sintered pellets, the exact phase composition could not be determined. From microstructural examination using backscattered electron imaging, there does seem to be a three phase composition similar to that found by Kim et al. that includes the perovskite Sr(Coi.xFex)02.5-5 in the form of rods or needles with SrFe1.5 xCoxO3.25-5 and (Co,Fe)304 visible as gray and black regions, respectively. From Fig. X, the fraction of the rod shaped perovskite seems larger than the traction present in solid state synthesis techniques this may be... 

Pt and Pd nitride nanoparticles have been synthesized by sputtering of the parent metal with N2 plasma [85]. Traditional solid-state synthesis techniques are often unsuccessful in creating Pt/Pd nitrides due to the low M-N bond strength. Physical vapor deposition processes such as sputtering can, however, often produce materials that are not expected thermodynamically due to the nature of the reaction. In this study, platinum and palladium thin films and nanoparticles were... 

Inorganic nanoparticles such as metal/semiconductors (M/SC) immobilized in polymer matrices have attracted considerable interest in recent years due to their distinct individualistic and cooperative properties [84]. Although the control of size and shape of M/SC nanoparticles has been widely investigated, the fundamental mechanism of nanostructural formation and evolution is still poorly understood. A novel cryochemical solid-state synthesis technique has been developed to produce M/SC nanocomposites [85]. This method is based on the low-temperature cocondensation of M/SC and monomer vapors, followed by the low-temperature solid-state polymerization of the cocondensates. As a result of the method of stabilizing the metal particle without requiring any specific coordination bonds between the particle surface and the polymer matrix, generated nanoparticles (Ag-nanocrystal mean size 50 A) were embedded in the polymer matrix with well-controlled shapes and a narrow size distribution [86]. 

An ideal replacement formulation would be a mixture of synthetic lipids, in a ratio based on a good understanding of their individual functions in LS, combined with simple peptide sequences, produced via solid-state synthesis techniques, which capture the full activity of the... 

The expansion in use of solid-state synthesis is of undoubted interest. These routes can be applied not only for obtaining complexes by the method of immediate interaction of components in the reaction of complex formation (Sec. 3.1), but also via modification of coordinated ligand systems (Sec. 3.3.2). To carry out this variant of template synthesis, it is worthwhile using the techniques of solid-state organic syntheses [9-11]. 

Solid-state synthesis is rich in the variety of techniques used to prepare materials. In this chapter some of the major methods used today will be presented and discussed. Some of these methods, such as direct combination, have been in use since the beginning of... 

A new family of high conductivity, mixed metal oxides having the pyrochlore crystal structure has been discovered. These compounds display a variable cation stoichiometry, as given by Equation 1. The ability to synthesize these materials is highly dependent upon the low temperature, alkaline solution preparative technique that has been described the relatively low thermal stability of those phases where an appreciable fraction of the B-sites are occupied by post transition element cations precludes their synthesis in pure form by conventional solid state reaction techniques. 

NMR spectroscopy is probably the most important method for elucidating the structure and bonding of all compounds descried in this chapter. As these compounds are often liquids or can easily be dissolved in organic solvents, the electronic behavior of single molecules can be studied in rather short times. Solid-state NMR techniques play a much less important role. However, NMR spectroscopy not only enables clarification of structural details but can also be used to follow the progress of reactions during the synthesis of known or unknown compounds. Furthermore, the... 

An important way of overcome the diffusion barrier in solid state synthesis is the technique of vapor transport, where an agent is added to the reactants to produce a volatile intermediate in a sealed tube. For example the formation of A12S3 is slow even at 800°C where A1 is liquid and S... 

A requirement for making YAG crystals is a homogeneous, high-purity starting material for use in the Czochralski technique. This means that the application of mechanical mixing and solid-state diffusion techniques are limited. Accordingly, a variety of synthesis techniques have been developed, most of which are sol-gel based. 

Rajeshwar and Secco (52,53) used DT A and other TA techniques to study the solid-state synthesis of 13 ammonium fluorolanthanates from Ln203 — NH4F reaction mixtures. Two types of fluorolanthanates appeared in the reaction products, NH4LnF4 and (NH4.)3Ln2F9. 

DNA libraries are obtained by a combination of the techniques of chemical solid-state synthesis and the combinatorial methods described later for peptides (see Sec. 9.3.2.2). DNA should, however, first be transformed to RNA libraries in order to yield useful recognition systems. Starting from a large pool of random-sequence DNA molecules, RNA sequences are obtained (see Fig. 8.4.3),... 

In 1963 Merrifield introduced solid-state synthesis for the synthesis of peptides. This technique involves chemical functionalization of a polystyrene bead that reacts with the carboxylic acid portion of a N-protected amino acid to give a polymer-bound amino ester such as 284. When 284 is treated with a reagent to deprotect the amine, it can react with another N-protected amino acid, activated at the carbonyl, to give a dipeptide. This procedure can be repeated to generate the desired polypeptide, and when the target has been attained a reagent is added to cleave the polypeptide from the bead (usually by hydrolysis). This solid-state synthesis can be applied to other types of chemical transformations. ... 

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