scholarly journals Determination of the Chemical Composition of Lithium Niobate Powders

Crystals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 340 ◽  
Author(s):  
Oswaldo Sánchez-Dena ◽  
Carlos J. Villagómez ◽  
César D. Fierro-Ruíz ◽  
Artemio S. Padilla-Robles ◽  
Rurik Farías ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Lithium Niobate ◽  
Single Crystals ◽  
Structure Refinement ◽  
Linear Equations ◽  
Powdered Material ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scattering Effects

Existent methods for determining the composition of lithium niobate single crystals are mainly based on their variations due to changes in their electronic structure, which accounts for the fact that most of these methods rely on experimental techniques using light as the probe. Nevertheless, these methods used for single crystals fail in accurately predicting the chemical composition of lithium niobate powders due to strong scattering effects and randomness. In this work, an innovative method for determining the chemical composition of lithium niobate powders, based mainly on the probing of secondary thermodynamic phases by X-ray diffraction analysis and structure refinement, is employed. Its validation is supported by the characterization of several samples synthesized by the standard and inexpensive method of mechanosynthesis. Furthermore, new linear equations are proposed to accurately describe and determine the chemical composition of this type of powdered material. The composition can now be determined by using any of four standard characterization techniques: X-Ray Diffraction (XRD), Raman Spectroscopy (RS), UV-vis Diffuse Reflectance (DR), and Differential Thermal Analysis (DTA). In the case of the existence of a previous equivalent description for single crystals, a brief analysis of the literature is made.

scholarly journals Rubidium tetrafluoridobromate(III): redetermination of the crystal structure from single-crystal X-ray diffraction data

IUCrData ◽  
2019 ◽  
Vol 4 (11) ◽  
Author(s):  
Artem V. Malin ◽  
Sergei I. Ivlev ◽  
Roman V. Ostvald ◽  
Florian Kraus
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Single Crystals ◽  
Diffraction Data ◽  
Structure Type ◽  
X Ray Diffraction ◽  
X Ray ◽  
Square Planar ◽  
Atomic Coordinates

Single crystals of rubidium tetrafluoridobromate(III), RbBrF4, were grown by melting and recrystallizing RbBrF4 from its melt. This is the first determination of the crystal structure of RbBrF4 using single-crystal X-ray diffraction data. We confirmed that the structure contains square-planar [BrF4]− anions and rubidium cations that are coordinated by F atoms in a square-antiprismatic manner. The compound crystallizes in the KBrF4 structure type. Atomic coordinates and bond lengths and angles were determined with higher precision than in a previous report based on powder X-ray diffraction data [Ivlev et al. (2015). Z. Anorg. Allg. Chem. 641, 2593–2598].

scholarly journals Determination of Chromite Sands Suitability for Use in Moulding Sands

2017 ◽  
Vol 17 (2) ◽  
pp. 107-110
Author(s):  
K. Stec ◽  
J. Podwórny ◽  
B. Psiuk ◽  
Ł. Kozakiewicz
Keyword(s):  
Phase Composition ◽  
High Temperature ◽  
Chemical Composition ◽  
Chemical Properties ◽  
Grinding Process ◽  
X Ray Diffraction ◽  
Scanning Microscope ◽  
Spectroscopy Technique ◽  
X Ray

Abstract Using the available analytical methods, including the determination of chemical composition using wavelength-dispersive X-ray fluorescent spectroscopy technique and phase composition determined using X-ray diffraction, microstructural observations in a highresolution scanning microscope equipped with an X-ray microanalysis system as well as determination of characteristic softening and sintering temperatures using high-temperature microscope, the properties of particular chromite sands were defined. For the study has been typed reference sand with chemical properties, physical and thermal, treated as standard, and the sands of the regeneration process and the grinding process. Using these kinds of sand in foundries resulted in the occurrence of the phenomenon of the molding mass sintering. Impurities were identified and causes of sintering of a moulding sand based on chromite sand were characterized. Next, research methods enabling a quick evaluation of chromite sand suitability for use in the preparation of moulding sands were selected.

Structure Determination of Al2CuMg Precipitates in Al-Cu-Mg Alloys by Structure Refinement and Quantitative Image Comparison

2000 ◽  
Vol 6 (S2) ◽  
pp. 1030-1031
Author(s):  
R. Kilaas ◽  
V. Radmilovic
Keyword(s):  
Structure Refinement ◽  
Metallic Phase ◽  
S Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Low Weight ◽  
Cell Dimensions ◽  
Quantitative Image ◽  
Unit Cell Dimensions

Al-Cu-Mg based alloys are of significant interest for aerospace and other applications, due to their low weight, mechanical strength and corrosion resistance. Their mechanical properties are based on a dispersion of S-phase precipitates, which have the composition Al2CuMg. The crystal structure of this inter-metallic phase has been studied using different diffraction techniques for more than five decades. While several models have been proposed for the structure of S-phase[l], only one of the previously proposed models were found to give a reasonable fit to our experimental data. This model, shown in Fig. 1 and given by Perlitz and Westgren (PW) [2] based on X-ray diffraction data, is orthorhombic with unit cell dimensions a = 0:4 nm, b = 0.923 nm, and c = 0.714 nm, space group Cmcm, containing 16 atoms in the ratio Al:Cu:Mg = 2:1:1.Several HREM images of S-phase precipitates located near the edge of the foil, Fig. 2, recorded along the [100]s and [010]s directions, were digitized from film and used for analysis.

scholarly journals Structural Evolution according to the temperature of the Compound LiNbO3

2014 ◽  
Vol 70 (a1) ◽  
pp. C1832-C1832
Author(s):  
Charef Tabti ◽  
Abdelkader Chouaih ◽  
Fodil Hamzaoui
Keyword(s):  
Data Structure ◽  
Lithium Niobate ◽  
Room Temperature ◽  
Structure Refinement ◽  
Structural Evolution ◽  
Structure Evolution ◽  
X Ray Diffraction ◽  
Reliability Factor ◽  
X Ray ◽  
Evolution Study

Structural evolution of LiNbO3 with temperature. A comparative study was made by X-ray diffraction on a single crystal of lithium niobate (LiNbO3) at low temperature (120K) and room temperature (293K). LiNbO3 is a ferroelectric compound particularly interesting for applications in the nonlinear optics field. After a recording of high resolution X-ray diffraction data, we used Blessing formalism for the reduction and the processing of the raw data. Structure refinement was carried out by program SHELXL. The results of the refinement led to a reliability factor of about 6% at T = 293K and of 3% at T = 120K. The structure evolution study of lithium niobate with temperature made it possible to highlight the compound stability in the investigated temperature range. Results show a light displacement (about 0.01Å) of oxygen atoms around the Li - Nb bond.

Growth and Structure of Zn1-xMnxCr2Se4 Single Crystals

2007 ◽  
Vol 130 ◽  
pp. 81-84 ◽  
Author(s):  
Izabela Jendrzejewska ◽  
Alicja Waśkowska ◽  
Elżbieta Augustyn
Keyword(s):  
Chemical Composition ◽  
Single Crystals ◽  
Cation Distribution ◽  
Chemical Vapour ◽  
Site Occupancy ◽  
Vapour Transport ◽  
X Ray Diffraction ◽  
X Ray ◽  
Chemical Vapour Transport ◽  
Tetrahedral Sites

The single crystals of ZnCr2Se4 spinel doped with manganese were prepared by the chemical vapour transport in closed silica tubes using stoichiometric contents of ZnSe, MnSe and CrCl3 as the transporting agent. Chemical composition of four single crystals of Zn-Mn-Cr-Se system with different concentration of manganese was analyzed and confirmed by X-ray diffraction study. The structure refinements, taking into account site occupancy factors, indicated that Mn ion shared tetrahedral sites with Zn ion. Thus, the formula describing cation distribution in the system is: Zn1-xMnxCr2Se4. For all x values equal to 0.12, 0.13, 0.18 and 0.24, the observed symmetry was cubic, space group Fd 3m .

scholarly journals Lithium Niobate Single Crystals and Powders Reviewed—Part I

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 973
Author(s):  
Oswaldo Sánchez-Dena ◽  
Cesar David Fierro-Ruiz ◽  
Sergio David Villalobos-Mendoza ◽  
Diana María Carrillo Flores ◽  
José Trinidad Elizalde-Galindo ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Chemical Composition ◽  
Lithium Niobate ◽  
Single Crystals ◽  
Accurate Determination ◽  
Indirect Methods ◽  
Methods Of Synthesis ◽  
Potential Applications ◽  
Historical Remarks

A review of lithium niobate single crystals and polycrystals in the form of powders has been prepared. Both the classical and recent literature on this topic are revisited. It is composed of two parts with sections. The current part discusses the earliest developments in this field. It treats in detail the basic concepts, the crystal structure, some of the established indirect methods to determine the chemical composition, and the main mechanisms that lead to the manifestation of ferroelectricity. Emphasis has been put on the powdered version of this material: methods of synthesis, the accurate determination of its chemical composition, and its role in new and potential applications are discussed. Historical remarks can be found scattered throughout this contribution. Particularly, an old conception of the crystal structure thought as a derivative structure from one of higher symmetry by generalized distortion is here revived.

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