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Thermally crystal structure

Figure 7.6. A filled. skutterudite antimonide crystal structure. A transition niclal atom (Fc or Co) at the centre of each octahedron is bonded to antimony atoms at each corner. The rare earth atoms (small spheres) are located in cages made by eight octahedra. The large thermal motion of rattling of the rare earth atoms in their cages is believed be responsible for the strikingly low thermal conductivity of these materials (Sales 1997). Figure 7.6. A filled. skutterudite antimonide crystal structure. A transition niclal atom (Fc or Co) at the centre of each octahedron is bonded to antimony atoms at each corner. The rare earth atoms (small spheres) are located in cages made by eight octahedra. The large thermal motion of rattling of the rare earth atoms in their cages is believed be responsible for the strikingly low thermal conductivity of these materials (Sales 1997).
A lomic Atomic Crystal structure Melting point (°C) Density Thermal conduc- tivity (W/m K- ) at 20 C Electrical resistivity Specific heat Thermal expansion Magnetic susceptibility Electrode potential w.r.i. sal calomel (V) z c 2... [Pg.865]

Atomic number Atomic weight Crystal structure Melting Density Thermal Electrical resistivity (at 20°C) Temperature coefficient of resistivity Specific Thermal Standard electrode potential Thermal neutron absorption cross-section. [Pg.882]

Since hydrofluoride synthesis is based on thermal treatment at relatively high temperatures, the possibility of obtaining certain fluorotantalates can be predicted according to thermal stability of the compounds. In the case of compounds whose crystal structure is made up of an octahedral complex of ions, the most important parameter is the anion-cation ratio. Therefore, it is very important to take in to account the ionic radius of the second cation in relation to the ionic radius of tantalum. Large cations, are not included in the... [Pg.46]

An irreversible extinction of the SHG signal at 150-200°C is observed for a number of other fluoride and oxyfluoride compounds of tantalum and niobium that crystallize in centrosymmetric space groups. This phenomenon is especially typical for the compounds prepared by precipitation from solutions [206]. The appearance of the weak SHG signal for such compounds is related to imperfections in their crystal structure and the creation of dipoles. Nevertheless, appropriate thermal treatment improves the structure and leads to the disappearance of dipoles and to the irreversible disappearance of the corresponding SHG signal. [Pg.230]

Thermal properties and decomposition mechanisms depend on the crystal structure type. Compounds with a crystal structure that includes shared octahedrons decompose forming tantalum- or niobium-containing gaseous components, while island-type compounds release light atoms and molecules into the gaseous phase. [Pg.339]

Unfortunately, the experimental data do not provide a definite answer to the nature of HVaqj. The hydronium ion, shown in Figure 11-5, does exist in certain crystal structures. Spectroscopic studies indicate that several species are present in water. Thermal and electrical con-... [Pg.187]

X-Ray diffraction from single crystals is the most direct and powerful experimental tool available to determine molecular structures and intermolecular interactions at atomic resolution. Monochromatic CuKa radiation of wavelength (X) 1.5418 A is commonly used to collect the X-ray intensities diffracted by the electrons in the crystal. The structure amplitudes, whose squares are the intensities of the reflections, coupled with their appropriate phases, are the basic ingredients to locate atomic positions. Because phases cannot be experimentally recorded, the phase problem has to be resolved by one of the well-known techniques the heavy-atom method, the direct method, anomalous dispersion, and isomorphous replacement.1 Once approximate phases of some strong reflections are obtained, the electron-density maps computed by Fourier summation, which requires both amplitudes and phases, lead to a partial solution of the crystal structure. Phases based on this initial structure can be used to include previously omitted reflections so that in a couple of trials, the entire structure is traced at a high resolution. Difference Fourier maps at this stage are helpful to locate ions and solvent molecules. Subsequent refinement of the crystal structure by well-known least-squares methods ensures reliable atomic coordinates and thermal parameters. [Pg.312]

In a similar manner, treatment of anhydrous rare-earth chlorides with 3 equivalents of lithium 1,3-di-ferf-butylacetamidinate (prepared in situ from di-ferf-butylcarbodiimide and methyllithium) in THF at room temperature afforded LnlMeCfNBuOils (Ln = Y, La, Ce, Nd, Eu, Er, Lu) in 57-72% isolated yields. X-ray crystal structures of these complexes demonstrated monomeric formulations with distorted octahedral geometry about the lanthanide(III) ions (Figure 20, Ln = La). The new complexes are thermally stable at >300°C, and sublime... [Pg.236]

Crystal structure and lattice parameters 6.7.2.4.3 Thermal stability 6.7.2.4.3... [Pg.648]


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See also in sourсe #XX -- [ Pg.206 , Pg.208 ]




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Thermal structure

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