Search results for "Oct"

High frequency dielectric relaxation in BaTio3derived materials

1992

Abstract A systematic study of the dielectric relaxation phenomenon has been carried out for ceramics with compositions derived from barium titanate in the frequency and temperature ranges 1 MHz–1 GHz and 250–500 K, respectively. Whatever the composition may be, a minimum of the relaxation frequency and a maximum of the dielectric dispersion appears at each phase transition temperature. The dipole-type relaxation is correlated to coherent displacements of the ions in the octahedron sites ordered either along chains or in 3D-lattice.

Structure and magnetic properties of AgFeP2O7

2010

Abstract AgFeP2O7 has been synthesized by flux crystallization and characterized by single crystal and powder X-ray diffraction (sp. gr. P21/c, a=7.3298(2), b=7.9702(2), c=9.5653(2) A, β=111.842(1)°, V=518.68(2) A3) and FTIR-spectroscopy. The structure is composed of isolated iron octahedra and phosphate tetrahedra interconnected into 3D network with hexagonal channels, where silver counter-ions are located. The magnetic behavior of the compound approaches the Curie–Weiss equation with a Weiss constant θ=−165.9 K indicating strong antiferromagnetic interaction between iron(III) ions.

Ferromagnetic exchange interaction in a new Ir(iv)-Cu(ii) chain based on the hexachloroiridate(iv) anion.

2019

The iridium(IV) complex (NBu4)2[IrCl6] (1) has been synthetised, characterised and used as a precursor to prepare the new chloro-bridged heterobimetallic IrIV–CuII chain of formula {IrCl5(μ-Cl)Cu(viim)4}n (2) [viim = 1-vinylimidazole]. The crystal structure and magnetic properties of 1 and 2 have been investigated. Both compounds crystallise in the monoclinic system with space group C2/c. Each IrIV ion in both 1 and 2 is six-coordinate and bonded to six chloride ions in a regular octahedral geometry. In compound 2, the CuII ion exhibits an axially elongated octahedron with four N atoms, from four monodentate viim ligands, that form the equatorial plane, and two chloride ions that occupy the…

Synthesis and catalytic performance in ethylene and 1-octene polymerization of chlorotitanium(IV) silsesquioxane complexes. Effect of increasing liga…

2016

Abstract The series of titanasilsesquioxanes that differ in a way of binding to the transition metal ( via one, two or three oxygen atoms) and type of nonreactive substituents bonded to inorganic oxygen-silicon cage ( i -Bu, Ph, c -C 6 H 11 ) were prepared by reacting of TiCl 4 with 1 eqv. of the silsesquioxane ligand. Upon treatment with an appropriate cocatalyst, all titanium precatalysts are active in ethylene and 1-octene polymerization and produce from low to high molecular weight polyethylenes and moderately ([ mmmm ] = 44–74%) isotactic poly(1-octene)s. The influence of polymerization parameters, type of cocatalyst and the silsesquioxane structure on the catalytic behavior of the tit…

First-principles calculations of the initial incorporation of carbon into flat and stepped Pd surfaces

2010

We employ density-functional-theory calculations to examine carbon adsorption and diffusion in Pd bulk, and on Pd(111) and Pd(211) surfaces. Different possible subsurface and on-surface structures are explored and the most stable structures are analyzed. We calculate various diffusion paths: lateral diffusion on a surface, migration to a subsurface region, and within the first interlayer. Our calculations show in accordance with the earlier theoretical results that on Pd(111) carbon prefers to adsorb on octahedral interstitial sites. On Pd(211) the fourfold hollow site under the step is energetically the most favorable one and the second best sites are the octahedral sites. The calculations…

Indium Doping in Barium Cerate: the Relation between Local Symmetry and the Formation and Mobility of Protonic Defects

2007

The solid solution series Ba(In,Ce)O3-ä has been investigated with respect to structure, formation, and mobility of protonic defects. Compared to the limited solubility of Y2O3 in BaCeO3 and BaZrO3, the complete solubility of In2O3 is suggested to reflect a relation between absolute hardness of the dopant and the ease of insertion into the hosting lattices. Extended X-ray absorption fine structure (EXAFS) was used to probe the local environment of In3+ in barium cerate: in the surroundings of the dopant, the orthorhombic structure is strongly modified, resulting in an increase of local symmetry. The InO6 octahedra are very regular, and there is no indication for any defect clustering. This …

Improvement of mechanical and dielectric properties of ethylene–octene copolymer by multi‐walled carbon nanotubes functionalized with poly(2,2′‐bithi…

2019

Extended x-ray absorption fine structure spectroscopy and first-principles study of SnWO4

2014

The local atomic structure in α- and β-SnWO 4 was studied bysynchrotron radiation W L 3 -edge X-ray absorption spectroscopy at 10 and 300 K.Strongly distorted WO 6 octahedra were found in α-SnWO 4 , whereas nearly regularWO 4 tetrahedra were observed in β-SnWO 4 , confirming previous results. Thestructural results obtained were supported by the first-principles calculations,suggesting that the second-order Jahn-Teller effect is responsible for octahedraldistortion.

Charge Transport in Trap-Sensitized Infrared PbS Quantum-Dot-Based Photoconductors: Pros and Cons

2018

Control of quantum-dot (QD) surface chemistry offers a direct approach for the tuning of charge-carrier dynamics in photoconductors based on strongly coupled QD solids. We investigate the effects of altering the surface chemistry of PbS QDs in such QD solids via ligand exchange using 3-mercaptopropionic acid (MPA) and tetrabutylammonium iodide (TBAI). The roll-to-roll compatible doctor-blade technique was used for the fabrication of the QD solid films as the photoactive component in photoconductors and field-effect phototransistors. The ligand exchange of the QD solid film with MPA yields superior device performance with higher photosensitivity and detectivity, which is due to less dark cur…

Organometal Halide Perovskites: Bulk Low-Dimension Materials and Nanoparticles

2015

Organometal halide perovskites (hybrid perovskites) contain an anionic metal–halogen-semiconducting framework and charge-compensating organic cations. As hybrid materials, they combine useful properties of both organic and inorganic materials, such as plastic mechanical properties and good electronic mobility related to organic and inorganic material, respectively. They are prepared from abundant and low cost starting compounds. The perovskite stoichiometry is associated with the dimensionality of its inorganic framework, which can vary from three to zero, 3D consisting of corner-sharing MX6 octahedra, and 0D consisting of isolated octahedra. Small-sized organic cations can fit into the MX6…