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.

The Role of Oxygen Ambience on the Optical Characteristics of ZnO Films

2013 ◽  
Vol 711 ◽  
pp. 26-31
Author(s):  
Feng Li ◽  
Ru Yuan Ma
Keyword(s):  
Grain Size ◽  
Oxygen Vacancies ◽  
Green Emission ◽  
Intensity Change ◽  
Zno Films ◽  
Radio Frequency Magnetron Sputtering ◽  
X Ray Diffraction ◽  
X Ray ◽  
Uv Emission

Zinc oxide (ZnO) films are grown by two methods-pulse laser deposition (PLD) and radio-frequency magnetron sputtering at various oxygen ambiences. Based on x-ray diffraction spectra and photoluminescence (PL) spectra, effects of the oxygen ambient on the grain size and emission properties of the ZnO films are investigated. For the samples grown by PLD, the PL spectrum consists of a single ultraviolet (UV) peak except one sample deposited at a low O2 pressure of 7 Pa. All the samples grown by sputtering have both a UV peak and a green emission. The disappearance of the green emission of the PLD samples is ascribed to deficiency of oxygen vacancies (Ov), and the green emission of the sample grown by sputtering is due to abundant Ov. The intensity change of the UV emission is due to the variation of exciton emission, which is related to grain size and stoichiometry. The position shifting of the UV peak of the PLD samples originates from the Zn interstitial-related degradation of stoichiometry.

scholarly journals Structure of strontium barium niobate Sr x Ba1 − x Nb2O6 (SBN) in the composition range 0.32 ≤ x ≤ 0.82

2006 ◽  
Vol 62 (6) ◽  
pp. 960-965 ◽  
Author(s):  
Sergey Podlozhenov ◽  
Heribert A. Graetsch ◽  
Julius Schneider ◽  
Michael Ulex ◽  
Manfred Wöhlecke ◽  
...  
Keyword(s):  
Tungsten Bronze ◽  
Site Occupancy ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Strontium Barium Niobate ◽  
Strontium Barium ◽  
Tetragonal Tungsten Bronze ◽  
Model Calculations ◽  
Cell Parameters

The structure of strontium barium niobate crystals Sr x Ba1 − x Nb2O6 is comprehensively studied in the whole range of the tetragonal tungsten bronze phase (x = 0.32–0.82) using both powder and single-crystal X-ray diffraction measurements. Unit-cell parameters, density, site-occupancy factors and interionic distances show an explicit composition dependence which can be consistently explained using simple model calculations. The temperature dependence of the unit-cell parameters exhibits a remarkable anisotropy in a broad temperature region below the phase transition temperature. This proves that the electrostrictive contribution to the thermal expansion plays an important role in strontium barium niobate.

scholarly journals Effect of Transition Metal on Structural and Dielectric Properties of Mg0.5Tm0.5Fe2O4 (Tm = Zn and Cu) System

2021 ◽  
Author(s):  
Pallavi Saxena ◽  
Anand Yadav
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Interfacial Polarization ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
High Frequencies ◽  
X Ray ◽  
Cubic Structure ◽  
High Dielectric

This study explored the structural and dielectric features of Mg0.5Tm0.5Fe2O4 (Tm = Zn and Cu) that were synthesized by the Solid-state reaction (SSR) method. The X-ray powder diffraction (XRD) analysis reveals that the prepared samples are single-phase cubic structure without any impurity. Rietveld-refined X-ray diffraction results reveal the formation of cubic structure and all the peaks of Mg0.5Zn0.5Fe2O4 and Mg0.5Cu0.5Fe2O4 are perfectly indexed in the cubic (Fd-3 m) structure. Dielectric constant and dielectric loss variation with frequency were also explored. Both decrease when the relevant alternating field is increasing and become constant at high frequencies which reflects the important role of interfacial polarization. Furthermore, the Mg0.5Cu0.5Fe2O4 having the smallest crystallite size (~ 44.73 nm) has a high dielectric constant (~ 4.41 × 104) value as compare to Mg0.5Zn0.5Fe2O4.

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.

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).

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.

Role of the Structure and Electronic Properties of Fe2O3-MoO3 Catalyst on the Dehydration of Isopropyl Alcohol

1993 ◽  
Vol 58 (7) ◽  
pp. 1591-1599 ◽  
Author(s):  
Abd El-Aziz A. Said
Keyword(s):  
Active Sites ◽  
Isopropyl Alcohol ◽  
Oxide Catalyst ◽  
Flow System ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Catalyst Composition ◽  
Surface Active

Molybdenum oxide catalyst doped or mixed with (1 - 50) mole % Fe3+ ions were prepared. The structure of the original samples and the samples calcined at 400 °C were characterized using DTA, X-ray diffraction and IR spectra. Measurements of the electrical conductivity of calcined samples with and without isopropyl alcohol revealed that the conductance increases on increasing the content of Fe3+ ions up to 50 mole %. The activation energies of charge carriers were determined in presence and absence of the alcohol. The catalytic dehydration of isopropyl alcohol was carried out at 250 °C using a flow system. The results obtained showed that the doped or mixed catalysts are active and selective towards propene formation. However, the catalyst containing 40 mole % Fe3+ ions exhibited the highest activity and selectivity. Correlations were attempted to the catalyst composition with their electronic and catalytic properties. Probable mechanism for the dehydration process is proposed in terms of surface active sites.

scholarly journals Modeling of magneto-conductivity of bismuth selenide: a topological insulator

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Yogesh Kumar ◽  
Rabia Sultana ◽  
Prince Sharma ◽  
V. P. S. Awana
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Single Crystal ◽  
Single Crystals ◽  
X Ray Diffraction ◽  
Field Range ◽  
X Ray ◽  
Bulk Carriers ◽  
Different Temperatures

AbstractWe report the magneto-conductivity analysis of Bi2Se3 single crystal at different temperatures in a magnetic field range of ± 14 T. The single crystals are grown by the self-flux method and characterized through X-ray diffraction, Scanning Electron Microscopy, and Raman Spectroscopy. The single crystals show magnetoresistance (MR%) of around 380% at a magnetic field of 14 T and a temperature of 5 K. The Hikami–Larkin–Nagaoka (HLN) equation has been used to fit the magneto-conductivity (MC) data. However, the HLN fitted curve deviates at higher magnetic fields above 1 T, suggesting that the role of surface-driven conductivity suppresses with an increasing magnetic field. This article proposes a speculative model comprising of surface-driven HLN and added quantum diffusive and bulk carriers-driven classical terms. The model successfully explains the MC of the Bi2Se3 single crystal at various temperatures (5–200 K) and applied magnetic fields (up to 14 T).

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