High-Order Incommensurate Modulations and Incommensurate Superstructures in Transparent Sr0.6Ba0.4Nb2O6(SBN40) Ceramics

1998 ◽  
Vol 31 (5) ◽  
pp. 683-691 ◽  
Author(s):  
Han-Young Lee ◽  
R. Freer
Keyword(s):  
Tungsten Bronze ◽  
Higher Order ◽  
Processing Route ◽  
Microstructural Development ◽  
X Ray Diffraction ◽  
Tetragonal Tungsten Bronze ◽  
Planar Defects ◽  
X Ray ◽  
Transmission Electron ◽  
Structural Modulation

Ceramics of strontium barium niobate (Sr0.6Ba0.4Nb2O6, SBN40), having the tetragonal tungsten bronze (TTB) structure, were prepared by a conventional processing route; sintering at temperatures in the range 1573–1723 K yielded products with three types of microstructure. Incommensurate superstructures were investigated by transmission electron microscopy (TEM). Modulation of the incommensurate superstructure (ICS) depended on microstructural development. The lowest-order ICS modulation was a common feature in all the SBN40 ceramics, regardless of microstructure. (h+1/2,h+1/2,l) reflections and unusually low δ (incommensurability parameter) were observed in SBN40 specimens having abnormally large grains and thus a certain degree ofA-site ordering was expected. Transparent SBN40 ceramics which exhibited large homogeneous grains were characterized by a shortenedcaxis, intense [001] X-ray diffraction reflections, a multiplication of (110) and (001) cell spacings and the appearance of higher-order ICS reflections. Planar defects, having the thickness of one d_{110} spacing, were observed aligned along \{110\}. The development of a higher-order structural modulation and of ICS reflections is believed to reduce the structural energy; the development of planar defects appears to stabilize the incommensurate phase.

Influence of Ti additions on the Texture and Dielectric Properties of LSBN-BST Complex Ceramics

1998 ◽  
Vol 541 ◽  
Author(s):  
J. Portelles ◽  
H. Amorín ◽  
J. M. Siqueiros ◽  
F.F. Castilión ◽  
E. Martínez ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Oxygen Vacancies ◽  
Tungsten Bronze ◽  
Material Structure ◽  
X Ray Diffraction ◽  
Strontium Barium ◽  
Tetragonal Tungsten Bronze ◽  
X Ray ◽  
First Results

AbstractThe stoichiometric La-Ti doped strontium-barium niobate ceramic system was obtained for different concentrations of Titanium ions (Ti=1,3,5,10,30,50 %), where the Nb5− was substituted by Ti4+ according to the following expression Sr0.255 La0.03Bao0.7Nb2−yTiyO6−y/2 (LSBN-BST). The oxygen vacancies thus created which, together with the vacancies in the A sites of the tetragonal tungsten-bronze (TTB) material structure, have an important influence on their texture and dielectric properties, due to the crucial role of the occupancy of the crystallographic sites. X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and thermoelectric analyses are reported. We report the first results for thin films of LSBNT- 7 % obtained by the PLD technique. The diffraction pattern reveals the presence of the LSBNT structure without annealing.

scholarly journals Characterization of K6Ta10.8O30 Microrods with Tetragonal Tungsten Bronze-Like Structure Obtained from Tailings from the Penouta Sn-Ta-Nb Deposit

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2289
Author(s):  
Belén Sotillo ◽  
Lorena Alcaraz ◽  
Félix A. López ◽  
Paloma Fernández
Keyword(s):  
Crystal Structure ◽  
Tungsten Bronze ◽  
X Ray Diffraction ◽  
Tetragonal Tungsten Bronze ◽  
X Ray ◽  
The North ◽  
Recovered Material ◽  
North Of Spain ◽  
Scanning Electron

In this work, a deep characterization of the properties of K6Ta10.8O30 microrods has been performed. The starting material used to grow the microrods has been recovered from mining tailings coming from the Penouta Sn-Ta-Nb deposit, located in the north of Spain. The recovered material has been submitted to a thermal treatment to grow the microrods. Then, they have been characterized by scanning electron microscopy, X-ray diffraction, micro-Raman and micro-photoluminescence. The results of our study confirm that the K6Ta10.8O30 microrods have a tetragonal tungsten bronze-like crystal structure, which can be useful for ion-batteries and photocatalysis.

Measurement of Debye-Waller factors of silicon as a function of temperature using energy-filtered CBED rocking-curve technique

1994 ◽  
Vol 52 ◽  
pp. 996-997
Author(s):  
S. Swaminathan ◽  
S. Altynov ◽  
I. P. Jones ◽  
N. J. Zaluzec ◽  
D. M. Maher ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Liquid Nitrogen Temperature ◽  
Convergent Beam Electron Diffraction ◽  
Higher Order ◽  
X Ray Diffraction ◽  
Beam Electron ◽  
X Ray ◽  
Crystal Potential ◽  
Transmission Electron ◽  
Convergent Beam

The advantages of quantitative Convergent Beam Electron Diffraction (CBED) method for x-ray structure factor determination have been reviewed by Spence. The CBED method requires accurate values of Debye-Waller (D-W) factors for the estimation of the coefficients of crystal potential of the higher order beams, Vg, the calculation of the absorption potential, V′g using the Einstein model for phonons, and finally the conversion of the fitted values of the coefficients of crystal potential, V″, to x-ray structure factors. Debye-Waller factors are conventionally determined by neutron or x-ray diffraction methods. Because of the difficulties in conducting high temperature neutron and x-ray diffraction experiments, D-W factors are rarely measured at temperatures above room temperature. Debye-Waller factors at high temperatures can be determined by Convergent Beam Electron diffraction (CBED) method using Transmission Electron Microscopy (TEM) employed with a hot stage attachment. Recently Holmestad et al. have attempted to measure the D-W factors by matching the energy-filtered Higher Order Laue Zone (HOLZ) line intensities near liquid nitrogen temperature.

Understanding Precursor Phenomena for the R-Phase Transformation in Ti-Ni-Based Alloys

MRS Bulletin ◽  
2002 ◽  
Vol 27 (2) ◽  
pp. 121-127 ◽  
Author(s):  
Daisuke Shindo ◽  
Yasukazu Murakami ◽  
Takuya Ohba
Keyword(s):  
Phase Transformation ◽  
Diffuse Scattering ◽  
Parent Phase ◽  
Martensitic Transformations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Displacements ◽  
Transmission Electron ◽  
Critical Issues ◽  
Structural Modulation

AbstractPrecursor phenomena are critical issues for martensitic transformations. In this article, we show recent progress in understanding precursor phenomena to the R-phase transformation, which is important for both fundamentals and applications. Structural modulation in the parent phase was intensively studied by means of detailed analyses of the weak diffuse scattering of electrons with the aid of recently developed energy-filtered transmission electron microscopy coupled with x-ray diffraction. A peculiar domain-like structure, which originates from static transverse atomic displacements in the parent phase, was discovered by virtue of these advanced methods. The characteristics of this structure (e.g., size, shape, and temperature-dependence), as well as its role in the subsequent R-phase transformation, are discussed.

Influence of Addition of Polymeric Precursors of Ceramics on Sintering of Al2O3

2012 ◽  
Vol 727-728 ◽  
pp. 1092-1097
Author(s):  
Ana Lúcia Exner Godoy ◽  
José Carlos Bressiani ◽  
Ana Helena de Almeida Bressiani
Keyword(s):  
Electron Microscopy ◽  
Ceramic Composites ◽  
Processing Route ◽  
Sintering Behavior ◽  
X Ray Diffraction ◽  
Sintering Aid ◽  
X Ray ◽  
Polymer Precursors ◽  
Transmission Electron ◽  
Indentation Analysis

The effects of adding polymer precursor on the sintering behavior, microstructure and hardness of alumina ceramics have been studied. Polymer sintering aid polymethylhidrogensiloxane were used for alumina based ceramics sintered at 1650º C. The sintered materials were characterized using: (a) helium picnometry to determine apparent density; (b) x-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy and energy dispersive x-ray spectrometry to determine the microstructure and composition; (c) Vickers indentation analysis to determine the hardness and fracture toughness. The addition of polymethylhidrogensiloxane yielded alumina/mullite composites. The preparation of ceramic composites using small amounts of polymer precursors is suited for alumina based ceramics. The processing route being simple, it has the potential to enable the manufacture of complex shaped pieces.

SrTiO3 films on platinized (0001) Al2O3: Characterization of texture and nonstoichiometry accommodation

2004 ◽  
Vol 19 (5) ◽  
pp. 1477-1486 ◽  
Author(s):  
Dmitri O. Klenov ◽  
Troy R. Taylor ◽  
Susanne Stemmer
Keyword(s):  
Surface Defects ◽  
X Ray Diffraction ◽  
Pt Electrode ◽  
Lattice Match ◽  
Planar Defects ◽  
X Ray ◽  
Grain Sizes ◽  
Transmission Electron ◽  
Pt Films

Transmission electron microscopy and x-ray diffraction were used to study SrTiO3 films grown on platinized (0001) Al2O3 substrates. The Pt films were epitaxial with an orientation relationship described by (111)Pt‖(0001)Al2O3 and [110]Pt‖[10¯10]Al2O3. SrTiO3 films with two different Sr to Ti ratios, 1.02 and 1.4, were deposited by radio-frequency magnetron sputtering. In the film with a large amount of Sr excess, the grain sizes were smaller and a high density of planar defects was observed. The films were predominantly (111) textured, but a weaker (110) texture component was also found, independent of stoichiometry. While the (111) texture could be explained with the excellent lattice match with (111) Pt, the (110) textured grains had a large mismatch with the Pt electrode. We propose that the presence of the (110) oriented grains is due to nucleation at Pt surface defects. Planar defects in the films with a large amount of Sr excess served to accommodate the nonstoichiometry. Comparison with homoepitaxial SrTiO3 films showed that the density of planar defects in the SrTiO3 films on (111)Pt/Al2O3 is insufficient to accommodate all the excess Sr. The influence of the film microstructure on the dielectric properties is also discussed.

X-ray diffraction data for the new ferroelectric tetragonal tungsten bronze phases, Ba2RETi2M3O15:M=Nb and RE=La, Pr, Nd, Sm, Gd, Dy, (Bi);M=Ta and RE=La, Nd

2005 ◽  
Vol 20 (1) ◽  
pp. 43-46 ◽  
Author(s):  
Gabrielle C. Miles ◽  
Martin C. Stennett ◽  
David Pickthall ◽  
Caroline A. Kirk ◽  
Ian M. Reaney ◽  
...  
Keyword(s):  
Diffraction Data ◽  
Tungsten Bronze ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
Tungsten Bronze Structure ◽  
Tetragonal Tungsten Bronze ◽  
X Ray ◽  
Anomalous Data ◽  
Tetragonal Unit Cell ◽  
Ion Radius

X-ray powder diffraction data are presented for nine new phases with the tetragonal tungsten bronze structure. By comparison with the structure of the M=Nb,RE=La analogue, these contain Ba in the large pentagonal sites with coordination number 15, a range of large rare-earth cations and Bi in the twelve coordinate sites, and the smaller cations, Ti and either Nb or Ta, in the octahedral framework sites. The a lattice parameter data of the tetragonal unit cell show an approximately linear variation with trivalent ion radius, apart from Dy, whose value appears to be anomalous; data for c show little variation with trivalent ion radius.

scholarly journals Structural Transition in Cu/Fe Multilayered Thin Films

1996 ◽  
Vol 441 ◽  
Author(s):  
Tai D. Nguyen ◽  
Alison Chaiken ◽  
Troy W. Barbee
Keyword(s):  
Layer Thickness ◽  
Ion Beam ◽  
Microstructural Development ◽  
Ion Beam Sputtering ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
X Ray ◽  
Transmission Electron ◽  
Beam Sputtering ◽  
Bcc Structure

AbstractMicrostructural development of Fe and Cu in Cu/Fe multilayers of layer thickness 1.5–10 nm prepared on Si, Ge, and MgO substrates by ion beam sputtering has been studied using x-ray diffraction and cross-sectional transmission electron microscopy (TEM). High-angle x-ray results show an fcc Cu structure and a distorted bcc structure in the Fe layers at 5 nm-layer-thickness and smaller, and bcc Fe (110) and fcc Cu (111) peaks in the 10 nm-layer-thickness samples. Lowangle x-ray diffraction indicates that the layers in the samples grown on MgO substrates have a more uniform and smooth layered structure than the multilayers grown on Si and Ge substrates, which results from larger grains in the MgO substrate samples for the same layer thickness. Relationships among growth, microstructure, and interfaces with layer thickness are discussed.

The Effect of Si Additions on the Epitaxial Growth of Gel−x Cx Alloys on Si(100)

1996 ◽  
Vol 440 ◽  
Author(s):  
Bi-Ke Yang ◽  
J. D. Weil ◽  
M. Krishnamurthy
Keyword(s):  
Epitaxial Growth ◽  
Molecular Beam ◽  
Layer Growth ◽  
Ex Situ ◽  
Growth Mechanisms ◽  
X Ray Diffraction ◽  
Planar Defects ◽  
X Ray ◽  
Transmission Electron

AbstractWe report on the differences in the epitaxial growth mechanisms between Ge1−xCx (O<x<0.1) and Ge1−x−ySixCy (x=0.2, 0<y<0.05) alloys grown on Si(100) using low temperature( 200°C) molecular beam epitaxy. Thin films (50˜65nm) were characterized in situ by RHEED and ex situ by transmission electron microscopy and x-ray diffraction. With increasing C concentration, the microstructure of both Ge and GeSi alloys changes from 2D layer growth to 3D islanding. The d400 spacing of the relaxed alloys decreases marginally, with a maximum of 1at.% C being substitutionally incorporated. Ge-C films with higher C content have a high density of planar defects, typically twins and stacking faults. The addition of 20% Si does not appear to increase the amount of substitutional C in the films. Rather, the additions of 20% Si to Ge-C alloys somehow seems to enhance the tendency for the formation of planar defects.

1 MV super-high-resolution electron microscopy of Nb2O5-WO3complex compounds with TTB type subcells

1978 ◽  
Vol 36 (1) ◽  
pp. 298-299
Author(s):  
Shigeo Horiuchi
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Composition Range ◽  
Tungsten Bronze ◽  
High Resolution Electron Microscopy ◽  
X Ray Diffraction ◽  
Tetragonal Tungsten Bronze ◽  
X Ray ◽  
Voltage Electron ◽  
Resolution Electron

It is known that, over a composition range in a Nb2-O5-WO3 system, the crystal structure of compounds is composed of subcells with tetragonal tungsten bronze ( TIB ) type.) Different models have however been reported for some of them. The crystals are usually prepared in sealed tubes and sometimes show different colours due to a reduction in spite of a definite starting composition. Moreover, they frequently include small domains, which make the structure analysis by x-ray diffraction very difficult. In the present study we examine a series of these compounds, prepared under various conditions, by a super-high-resolution, high-voltage electron microscope ( Hitachi 1250 ),in which the lattice fringes of 2.0 Å in width can be resolved at an accelerating voltage of 1 MV under an axial illumination with equipping a specimen goniometer.2)Fig.l is a crystal structure image of 4Nb2O5.9WO3. According to electron diffractions the lattice parameters are a=12.3, b=36.6 and c=3.94 Å (orthorhombic).

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