Analysis of Antimony-Tin-Based Skutterudites

1998 ◽  
Vol 545 ◽  
Author(s):  
S. B. Schujman ◽  
G. A. Slack ◽  
H. C. Nguyen ◽  
G. S. Nolas ◽  
R. A. Young ◽  
...  
Keyword(s):  
Cross Sections ◽  
Mixed Valence ◽  
Partial Replacement ◽  
X Ray Diffraction ◽  
Extra Charge ◽  
Semiconducting Properties ◽  
Wide Range ◽  
Diffraction Patterns ◽  
The Stability ◽  
Unit Cell Constant

AbstractSince the proposal of skutterudites as possible Phonon-Glass, Electron-Crystal materials, a lot of work has been done trying to fill the structural voids with foreign “rattling” atoms. In order to keep the electronic count per unit cell constant (and thus, the semiconducting properties of most of the compounds under study) partial replacement of either the cation or the anion in the original formula by an appropriate neighbor in the periodic table is an option. In the case of antimonides, replacing part of the Sb with Ge or Sn in order to compensate the extra charge introduced by void fillers has proved useful for compounds based on rare-earth filled IrSb3. In the case of RhSb3, we found that large quantities of Sn can be incorporated into the skutterudite structure of RhSb3 without either filling the voids or producing charge carriers.We have analyzed the stability of several cross-sections of the Rh-Sb-Sn ternary system and have found a wide range of compositions with the basic skutterudite structure as we vary the Sn content. In all the cases, the tin goes substitutionally into the antimony sites. The voids remain empty. Density measurements suggest the existence of metal vacancies, confirmed by Rietveld refinement of the powder X-ray diffraction patterns. The possibility of Sn-induced mixed-valence of Rh on the anion sites is being investigated.

The crystallography of calf rennin (chymosin)

1971 ◽  
Vol 178 (1052) ◽  
pp. 245-258 ◽  
Keyword(s):  
Degradation Products ◽  
Protein Solutions ◽  
Stable Range ◽  
X Ray Diffraction ◽  
Stable Species ◽  
Wide Range ◽  
Unit Cells ◽  
Diffraction Patterns ◽  
The Stability ◽  
Ph Range

The growth of crystals of calf rennin (chymosin, † EC 3.4.4.3) and the control of nucleation to produce crystals of desired size, are described. Only one stable species, orthorhombic rennin I, has been found, but a metastable monoclinic species, rennin II, appeared on one occasion in a solution nearly saturated with glycine. The morphology, optical characteristics and unit cells of these species are recorded. In rennin I, small differences in the properties of sectors built by deposition on the three types of crystal faces are attributed to differences in the proportions of either degradation products or of the slightly different isoenzymes known to be present in calf rennin. Rennin I crystals have been obtained only within the pH range of greatest stability of the protein, 5. 0 to 6. 2; but the crystals tolerate subsequent changes of pH down to 2. 0. The stability of crystals appears to be much greater than that of salt-free protein solutions. Rennin I may be crosslinked with glutaraldehyde with no loss of order, giving crystals stable over a wide range of solution conditions, including pH 2.0 to 10.0 and salt-free solutions. The remarkable swelling behaviour when the pH is raised beyond the stable range is described. Rennin II, though monoclinic in symmetry, shows in its X -ray diffraction patterns strong evidence of a pseudo-orthorhombic arrangement of molecules.

Physical and Mechanical Properties of Cement Paste Were Used Partially with Fly Ash and Kaolin Waste

2017 ◽  
Vol 866 ◽  
pp. 199-203
Author(s):  
Chidchanok Chainej ◽  
Suparut Narksitipan ◽  
Nittaya Jaitanong
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Room Temperature ◽  
Physical And Mechanical Properties ◽  
Partial Replacement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lime Water ◽  
Diffraction Patterns ◽  
Iron Mold

The aims of this research were study the microstructures and mechanical properties for partial replacement of cement with Fly ash (FA) and kaolin waste (KW). Ordinary Portland cement were partially replaced with FA and KW in the range of 25-35% and 10-25% by weight of cement powder. The kaolin waste was ground for 180 minutes before using. The specimen was packing into an iron mold which sample size of 5×5×5 cm3. Then, the specimens were kept at room temperature for 24 hours and were moist cured in the incubation lime water bath at age of 3 days. After that the specimens were dry cured with plastic wrap at age of 3, 7, 14 and 28 days. After that the compounds were examined by x-ray diffraction patterns (XRD) and the microstructures were examined by scanning electron microscopy (SEM). The compressive strength was then investigated.

2D X-ray diffraction and molecular modelling of the crystalline structure of polyesters under uniaxial stress

2021 ◽  
pp. 096739112199822
Author(s):  
Ahmed I Abou-Kandil ◽  
Gerhard Goldbeck
Keyword(s):  
Crystalline Structure ◽  
Molecular Modelling ◽  
Three Dimensional ◽  
Uniaxial Stress ◽  
X Ray Diffraction ◽  
X Ray ◽  
Wide Range ◽  
Modelling Techniques ◽  
Diffraction Patterns

Studying the crystalline structure of uniaxially and biaxially drawn polyesters is of great importance due to their wide range of applications. In this study, we shed some light on the behaviour of PET and PEN under uniaxial stress using experimental and molecular modelling techniques. Comparing experiment with modelling provides insights into polymer crystallisation with extended chains. Experimental x-ray diffraction patterns are reproduced by means of models of chains sliding along the c-axis leading to some loss of three-dimensional order, i.e. moving away from the condition of perfect register of the fully extended chains in triclinic crystals of both PET and PEN. This will help us understand the mechanism of polymer crystallisation under uniaxial stress and the appearance of mesophases in some cases as discussed herein.

scholarly journals Iron-containing phases in metallurgical and coke dusts as well as in bog iron ore

Nukleonika ◽  
2017 ◽  
Vol 62 (2) ◽  
pp. 187-195 ◽  
Author(s):  
Tadeusz Szumiata ◽  
Marzena Rachwał ◽  
Tadeusz Magiera ◽  
Katarzyna Brzózka ◽  
Małgorzata Gzik-Szumiata ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Spinel Structure ◽  
Iron Ore ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mineral Phases ◽  
Coke Plants ◽  
Wide Range ◽  
Specific Magnetic Susceptibility ◽  
Diffraction Patterns

Abstract Several samples of dusts from steel and coke plants (collected mostly with electro filters) were subjected to the investigation of content of mineral phases in their particles. Additionally, sample of bog iron ore and metallurgical slurry was studied. Next, the magnetic susceptibility of all the samples was determined, and investigations of iron-containing phases were performed using transmission Mössbauer spectrometry. The values of mass-specific magnetic susceptibility χ varied in a wide range: from 59 to above 7000 × 10−8 m-3·kg−1. The low values are determined for bog iron ore, metallurgical slurry, and coke dusts. The extremely high χ was obtained for metallurgical dusts. The Mössbauer spectra and X-ray diffraction patterns point to the presence of the following phases containing iron: hematite and oxidized magnetite (in coke and metallurgical dusts as well as metallurgical slurry), traces of magnetite fine grains fraction (in metallurgical dusts), amorphous glassy silicates with paramagnetic Fe3+ and Fe2+ ions, traces of pyrrhotite (in coke dusts), α-Fe and nonstoichiometric wüstite (in metallurgical slurry), as well as ferrihydrite nanoparticles (in bog iron ore). For individual samples of metallurgical dusts, the relative contributions of Fe2+/3+ ions in octahedral B sites and Fe2+ ions in tetrahedral A sites in magnetite spinel structure differs considerably.

Ferroelectric and Ferromagnetic Properties of Co-doped BiFeO3 Thin Films

2010 ◽  
Vol 1256 ◽  
Author(s):  
Danilo G Barrionuevo ◽  
Surinder P Singh ◽  
Ram S Katiyar ◽  
Maharaj S. Tomar
Keyword(s):  
Thin Films ◽  
Magnetic Coupling ◽  
Partial Replacement ◽  
Material System ◽  
X Ray Diffraction ◽  
X Ray ◽  
Si Substrates ◽  
Solution Route ◽  
Diffraction Patterns ◽  
Novel Devices

AbstractMaterials which possess electrical and magnetic coupling are of great interest for novel devices. Bi(Fe1-xCox)O3 (BFCO) material system was synthesized by solution route for various compositions and thin films were prepared by spin coating on Pt (Pt/Ti/SiO2/Si) substrates. Structural properties of the films were investigated by x-ray diffraction and Raman spectroscopy. X-ray diffraction patterns confirms intense (110) in BiFeO3 and Bi(Fe1-xCox)O3 with rhombohedra distorted perovskite structure without impure phase. Bi(Fe1-xCox)O3 films show week ferroelectric polarization and ferromagnetism at room temperature. Ferroelectric and ferromagnetic coupling could be attributed to the elimination of oxygen vacancies and increased stress in the crystal structure by partial replacement of Fe2+ ion by Co2+ ion.

scholarly journals Defect-assisted synthesis of magneto-plasmonic silver-spinel ferrite heterostructures in a flower-like architecture

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Marco Sanna Angotzi ◽  
Valentina Mameli ◽  
Claudio Cara ◽  
Vincenzo Grillo ◽  
Stefano Enzo ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Spinel Ferrite ◽  
High Resolution Electron Microscopy ◽  
Careful Study ◽  
X Ray Diffraction ◽  
High Concentration ◽  
Resolution Electron ◽  
Wide Range ◽  
Controlled Morphology ◽  
Diffraction Patterns

Abstract Artificial nano-heterostructures (NHs) with controlled morphology, obtained by combining two or more components in several possible architectures, make them suitable for a wide range of applications. Here, we propose an oleate-based solvothermal approach to design silver-spinel ferrite flower-like NHs. Small oleate-coated silver nanoparticles were used as seeds for the growth of magnetic spinel ferrite (cobalt ferrite and spinel iron oxide) nanodomains on their surface. With the aim of producing homogeneous flower-like heterostructures, a careful study of the effect of the concentration of precursors, the reaction temperature, the presence of water, and the chemical nature of the spinel ferrite was carried out. The magnetic and optical properties of the NHs were also investigated. A heterogeneous growth of the spinel ferrite phase on the silver nanoparticles, through a possible defect-assisted mechanism, was suggested in the light of the high concentration of stacking faults (intrinsic and twins) in the silver seeds, revealed by Rietveld refinement of powder X-ray diffraction patterns and High-Resolution electron microscopy.

scholarly journals Preparation of CoFe2O4/SiO2Nanocomposites at Low Temperatures Using Short Chain Diols

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Thomas Dippong ◽  
Erika Andrea Levei ◽  
Oana Cadar
Keyword(s):  
Low Temperatures ◽  
Sol Gel ◽  
Silica Matrix ◽  
Short Chain ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nanocrystallite Size ◽  
Methylene Groups ◽  
Diffraction Patterns ◽  
The Stability

The preparation of 70% CoFe2O4/30% SiO2(wt%) nanocomposites by sol-gel method using three short chain diols (1,2-ethanediol, 1,3-propanediol, and 1,4-butanediol) as chelators was studied. The Fourier transformed infrared spectra and X-ray diffraction patterns were used to confirm the formation of nanocomposites. The X-ray diffraction analysis showed that the chain length of the carboxylates embedded in the silica matrix influences the formation of crystallized cobalt ferrite as single phase at low temperatures. The influence of the methylene groups number in the precursors and annealing temperature on the nanocrystallite size was revealed. The stability of the obtained compounds was determined by calculation of thermodynamic parameters.

scholarly journals Structures and thermal stability of the α-LiNH4SO4 polytypes doped with Er3+ and Yb3+

2017 ◽  
Vol 73 (1) ◽  
pp. 122-133 ◽  
Author(s):  
N. P. Sabalisck ◽  
C. Guzmán-Afonso ◽  
C. González-Silgo ◽  
M. E. Torres ◽  
J. Pasán ◽  
...  
Keyword(s):  
Single Crystals ◽  
Slow Evaporation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Wide Range ◽  
Cyclic Temperature ◽  
Polymorphic Forms ◽  
The Stability ◽  
Thermal Stability Of

In order to clarify the polymorphism in the lithium sulfate family, LiRE x (NH4)1 − x SO4 (0.5 ≤ x ≤ 4.0 mol%, nominal value; RE = Er3+, Yb3+ and Dy3+) crystals were grown from aqueous solution by slow evaporation between 298 and 313 K. The doping of the samples allowed us to obtain two polymorphic forms, α and β, of LiNH4SO4 (LAS). By means of X-ray diffraction (XRD) in single crystals, we determined the crystal structures of two new α-polytypes, which we have named α1- and α2-LAS. They present the same space group P21/c and the following relation among their lattice parameters: a 2 = −c 1, b 2 = −b 1, c 2 = −2a 1 − c 1. In order to evaluate the stability of the new α-polytypes, we performed thermal analysis, X-ray diffraction and dielectric spectroscopy on single crystals and polycrystalline samples over the cyclic temperature range: 190 → 575  → 190 K. The results obtained by all the techniques used in this study demonstrate that α-polytypes are stable across a wide range of temperatures and they show an irreversible phase transition to the paraelectric β-phase above 500 K. In addition, a comparative study of α- and β-polytypes shows that both polymorphic structures have a common axis, with a possible intergrowth that facilitates their coexistence and promotes the reconstructive α → β transition. This intergrowth was related to small anomalies detected between 240 and 260 K, in crystals with an α-habit.

Investigations on Dielectric phase transition behavior of Pb(Fe0.5-xScx)Nb0.5O3 Multiferroic Ceramics

MRS Advances ◽  
2016 ◽  
Vol 1 (9) ◽  
pp. 585-590
Author(s):  
Bandi Mallesham ◽  
Ranjith Ramadurai
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Essential Feature ◽  
Low Frequency ◽  
Cation Ordering ◽  
X Ray Diffraction ◽  
Dielectric Phase ◽  
Diffraction Patterns ◽  
The Stability

ABSTRACTPhase pure Pb[(Fe0.5-xScx)Nb0.5]O3 [x = 0 to 0.5] multiferroic relaxors have been synthesized to study the effect of Sc on dielectric phase tansition. Rietveld refinement of x-ray diffraction patterns confirm that the structure transforms from monoclinic (Cm) to rhomobohedral (R3m) at x = 0.3. Absence of low frequency dielectric response in compositions with low Sc content attributed to interfacial polarizabilty arising due to differences in conductivities of grain and grain boundary. Moreover, value of diffusivity parameter (γ) of high of Sc content compositions is near to 2, confirms relaxor charactertistic of these compositions. However, an essential feature of relaxors i.e., frequency dependent dielectric permittivity as a function of temperature is observed only in x = 0.5 composition [Pb(Sc0.5Nb0.5)O3 (PSN)]. In addition, ferroelectric phase transition temperature (Tmax) increases initially at lower Sc content (upto x ≤ 0.25), and further drops beyond x ≥ 0.3. Such behavior of Tmax in these compositions is due to the onset of B'-B" local cation ordering at x = 0.3. High temperature Raman spectra of Pb(Sc0.5Nb0.5)O3 (x = 0.5) confirm the stability of cation ordering in compositions with high Sc content well above the phase transition temperature.

The stability and screw sense of the α -helix in poly- β -benzyl-L-aspartate

1960 ◽  
Vol 259 (1296) ◽  
pp. 110-128 ◽  
Keyword(s):  
Optical Rotatory Dispersion ◽  
Molecular Models ◽  
X Ray Diffraction ◽  
X Ray ◽  
Left Handed ◽  
The Difference ◽  
Diffraction Patterns ◽  
The Stability ◽  
Α Helix ◽  
The Right

A number of polymers and copolymers containing β -benzyl-L-aspartate has been prepared and their optical rotatory dispersion in a variety of solvents has been measured. The results of these measurements together with studies of infra-red spectra, X-ray diffraction patterns, deuteration rates and molecular models lead to the following conclusions. (i) The α -helical form of poly- β -benzyl-L-aspartate is considerably less stable relative to the solvated randomly coiled form than that of poly- γ -benzyl-L-glutamate. (ii) The left-handed α -helix of poly- β -benzyl-L-aspartate is more stable than the right-handed one. (iii) The difference in stability between the two senses of α -helix is much less in the case of poly- β -benzyl-L-aspartate than in that of poly- γ -benzyl-L-glutamate or poly-L-alanine.

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