Single crystal

About: Single crystal is a research topic. Over the lifetime, 59617 publications have been published within this topic receiving 870828 citations.

ESR of Cu2+(H2O)6. II. A quantitative study of the dynamic Jahn‐Teller effect in copper‐doped zinc Tutton's salt

Abstract: The X‐band ESR spectra of 63Cu2+ doped zinc Tutton's salt enriched to 16 at.% in 17O isotope was studied in a single crystal at 20, 77, and 290°K. The powder spectrum of the same material was studied over the temperature range 10–350°K at X band and 120–290°K at Q band. The observed values of the g tensor and 63Cu and 17O hyperfine tensors were found to be strongly temperature dependent except when the magnetic field was parallel to g3, one of the principal axes of the g tensor. The directions of the principal axes of the g tensor and 63Cu hyperfine tensor were shown to be temperature independent, in opposition to the findings of other workers. In the single crystal, marked mI dependent linewidth variations in the 63Cu hyperfine components were observed in the temperature range 14–80°K, except when the external field was parallel to g3. The experimental data are explicable in terms of a dynamic Jahn‐Teller effect, in contrast to the previously held assumption that dilute copper Tutton's salt is a static Jahn‐Teller system. The energy splittings between the three inequivalent valleys were determined directly from the experimental results and found to be δ1,2 = 75 cm−1, δ1,3 ≃ 450 cm−1. The splittings are discussed in terms of published crystallographic data on Tutton's salts, and a crystal field calculation gave a value of δ1,2/δ1,3 = 1/5 in good agreement with experiment. The rate of intervalley jumping between the lowest two valleys was determined from linewidth measurements and found to be characteristic of an Orbach process, following the law τ = τ0 exp(120/k T). The value of 120 cm−1 is identified with the height of the ``warping'' barrier between valleys 1 and 2. Phonon‐assisted tunneling makes no significant contribution to the jumping rate.

MOCVD-derived highly transparent, conductive zinc- and tin-doped indium oxide thin films: precursor synthesis, metastable phase film growth and characterization, and application as anodes in polymer light-emitting diodes.

Abstract: Four diamine adducts of bis(hexafluoroacetylacetonato)zinc [Zn(hfa)2·(diamine)] can be synthesized in a single-step reaction. Single crystal X-ray diffraction studies reveal monomeric, six-coordinate structures. The thermal stabilities and vapor phase transport properties of these new complexes are considerably greater than those of conventional solid zinc metal−organic chemical vapor deposition (MOCVD) precursors. One of the complexes in the series, bis(1,1,1,5,5,5-hexafluoro-2,4-pentadionato)(N,N‘-diethylethylenediamine)zinc, is particularly effective in the growth of thin films of the transparent conducting oxide Zn−In−Sn−O (ZITO) because of its superior volatility and low melting point of 64 °C. ZITO thin films with In contents ranging from 40 to 70 cation % (a metastable phase) were grown by low-pressure MOCVD. These films exhibit conductivity as high as 2900 S/cm and optical transparency comparable to or greater than that of commercial Sn-doped indium oxide (ITO) films. ZITO films with the nominal c...

Crystal structure and magnetic properties of an octacyanometalate-based three-dimensional tungstate(V)-manganese(II) bimetallic assembly.

Abstract: A single crystal of the title compound [MnII6(H2O)9{WV(CN)8}4·13H2O]n was synthesized in a hot aqueous solution containing octacyanotungstate, Na3[W(CN)8]·3H2O, and Mn(ClO4)2·6H2O. The compound crystallized in the monoclinic system, space group P21/c with cell constants a = 15.438(2) A, b= 14.691(2) A, c = 33.046(2) A, β = 94.832(9)°, and Z = 4. The crystal consists of a WV−CN−MnII linked three-dimensional network [{MnII(H2O)}3{MnII(H2O)2 }3{WV(CN)8}4]n and H2O molecules as crystal solvates. There are two kinds of W sites: one is close to a dodecahedron geometry with six bridging and two terminal CN ligands; the other is close to a bicapped trigonal prism with seven bridging and one terminal CN ligands. The field-cooled magnetization measurement showed that the compound exhibits a spontaneous magnetization below Tc = 54 K. Further magnetization measurements on the field dependence reveal it to be a ferrimagnet where all of the Mn II ions are antiparallel to all the WV ions.

Morphological control of particles

Abstract: The objective of this review is to highlight the theoretical and practical aspects of particle morphological control. Materials with directional properties are opening new horizons in material science. Structural, optical, and electrical properties can be greatly augmented by the fabrication of composite materials with anisotropic microstructures or with anisotropic particles uniformly dispersed in an isotropic matrix. Examples include structural composites, magnetic and optical recording media, photographic film, and certain metal and ceramic alloys. The new applications and the need for model particles in scientific investigations are rapidly outdistancing the ability to synthesize anisotropic particles with specific chemistries and narrowly distributed physical characteristics (e.g. size distribution, shape, and aspect ratio). Anisotropic particles of many compositions have been produced but only a few (γ-Fe2O3 and AgI) are produced with any degree of chemical and physical control. These two examples are the result of literally decades of study. Unfortunately, the science and technology (mainly the technology) that have evolved are maintained as proprietary information. Thus, while we generally know what systems yield single crystal, anisotropic-shaped particles, we do not know how to make powders of these crystals with the desired control of shape uniformity, aspect ratio and phase composition. Particle shape control is a complex process requiring a fundamental understanding of the interactions between solid state chemistry, interfacial reactions and kinetics, and solution (or vapor) chemistry. During synthesis of other than a large single crystal the parameters controlling crystal growth must be balanced with the requirements for anisotropic powder nucleation and growth. Although there has been considerable progress in large single crystal growth and the synthesis of powders composed of monodispersed, spherical particles, these efforts have not often been transferred to the synthesis of anisotropic particles.