Studies on the perovskite-based La4Srn−4TinO3n+2

2003 ◽  
Vol 801 ◽  
Author(s):  
Jesús Canales-Vázquez ◽  
Shawen Tao ◽  
Mikhail Patrakeev ◽  
John T. S. Irvine ◽  
Wuzong Zhou ◽  
...  
Keyword(s):  
Layered Structure ◽  
Homologous Series ◽  
Short Range ◽  
Total Conductivity ◽  
Structural Characterisation ◽  
Linear Defects ◽  
Reducing Conditions ◽  
Oxygen Excess ◽  
Nominal Stoichiometry

AbstractPerovskite titanates with nominal stoichiometry ABO3+Δ are frequently reported in SOFC literature as having O3 stoichiometry. Such phases often exhibit quite interesting properties, but are not stoichiometric and the structural characterisation is usually not rigorous. Here we demonstrate how oxygen excess can be incorporated in a titanate perovskite-based lattice as crystallographic oxygen shears giving rise to the homologous series La4Srn−4TinO3n+2. The layered structure is lost for the n=12 member (La4Sr8Ti12O38−Δ), although the oxygen excess is accommodated within the perovskite framework in randomly distributed short-range linear defects. This compound was studied as potential fuel electrode due to its high total conductivity and stability in the most reducing conditions.

CHARACTERISATION OF Al DEFECTS IN SmBa2Cu3-XAlXO6+δ SUPERCONDUCTOR

2003 ◽  
Vol 17 (04n06) ◽  
pp. 936-941 ◽  
Author(s):  
M. SCAVINI ◽  
L. MOLLICA ◽  
R. BIANCHI ◽  
G. A. COSTA ◽  
M. FERRETTI ◽  
...  
Keyword(s):  
Phase Transition ◽  
Short Range ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Orthorhombic Phase ◽  
Superconducting Phase ◽  
Al Doping ◽  
X Ray ◽  
Reducing Conditions ◽  
Almost All

We present here a study on the effect of Al doping on the stucture of SmBa 2 Cu 3-X Al X O 6+δ (Sm-123) superconductor. Electron MicroProbe Analysis (EMPA) and X-Ray Powder Diffraction (XRPD) have revealed that the limit of a aluminium solubility x is between 0.5 and 0.6. For further doping BaAl 2 O 4 appears besides the superconducting phase. XRPD analysis on samples annealed in both oxidising and reducing conditions have revealed that the Al doping inhibits the tetragonal to orthorhombic phase transition. Nuclear Magnetic Resonance (NMR) analysis has shown that almost all the Al ions are coordinated tetrahedrally. The comparison between oxygen non-stoichiometry in pure and Al doped SmBa 2 Cu 3-X Al X O 6+δ suggests that the Al ions are ordered in clusters. A model is proposed for short-range order around Al doping ions which allows us to interpret the phase transition inhibition.

Pearl – A Nano-Composite & Natural Super Dielectric

2011 ◽  
Vol 11 ◽  
pp. 1-12 ◽  
Author(s):  
S.S. Pradhan ◽  
A. Sarkar
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Constant ◽  
Layered Structure ◽  
Nano Particles ◽  
Static Dielectric Constant ◽  
Total Conductivity ◽  
Nano Composite ◽  
High Polarization ◽  
Functional Nature ◽  
Very High

Pearl is a bio-originated valuable natural gem and it is also cultivated or harvested for jewellery. In this paper, the material aspects of pearl have been investigated experimentally and it has been found that it has a very high static dielectric constant ~ 105. The functional nature of the material is also established in this work. The beautiful lustre of natural pearl is explained by nano-optics and the layered structure of the material. The origin of super-dielectric nature of pearl has been explained by lightning rod effect (LRE) that causes ultra-high polarization of the dielectric background. The LRE is due to the presence of very small sized nano-particles in the natural pearl. Its electrical conductivity is mostly ionic, only less than 10% of the total conductivity is electronic. The scope of tailoring of its electro-activity has been probed.

The synthesis and structural characterisation of an homologous series of group 14 1-chloro-2,2-difluorovinyl compounds

2004 ◽  
Vol 125 (7) ◽  
pp. 1099-1103 ◽  
Author(s):  
A.K Brisdon ◽  
I.R Crossley ◽  
J.A Greenall ◽  
R.G Pritchard ◽  
J.E Warren
Keyword(s):  
Homologous Series ◽  
Group 14 ◽  
Structural Characterisation

Application of Modified Bloch Waves to Image Analysis of Extended Linear Defects

1974 ◽  
Vol 32 ◽  
pp. 402-403
Author(s):  
S. Nakahara ◽  
D. M. Maher
Keyword(s):  
Image Analysis ◽  
Computational Approach ◽  
Dislocation Loops ◽  
Plane Wave Expansion ◽  
Dynamical Equations ◽  
Bloch Waves ◽  
Linear Defects ◽  
Imperfect Crystal ◽  
Localized Defects ◽  
Defective Crystals

Since Head first demonstrated the advantages of computer displayed theoretical intensities from defective crystals, computer display techniques have become important in image analysis. However the computational methods employed resort largely to numerical integration of the dynamical equations of electron diffraction. As a consequence, the interpretation of the results in terms of the defect displacement field and diffracting variables is difficult to follow in detail. In contrast to this type of computational approach which is based on a plane-wave expansion of the excited waves within the crystal (i.e. Darwin representation ), Wilkens assumed scattering of modified Bloch waves by an imperfect crystal. For localized defects, the wave amplitudes can be described analytically and this formulation has been used successfully to predict the black-white symmetry of images arising from small dislocation loops.

In situ TEM Studies of agglomeration of sub-nanometer Ru layers in Ru/C multilayers

1992 ◽  
Vol 50 (1) ◽  
pp. 256-257
Author(s):  
Tai D. Nguyen ◽  
Ronald Gronsky ◽  
Jeffrey B. Kortright
Keyword(s):  
Layered Structure ◽  
Driving Force ◽  
High Energy ◽  
Superior Performance ◽  
In Situ Tem ◽  
Rayleigh Instability ◽  
Practical Applications ◽  
Transmission Electron ◽  
Diffraction Patterns

Nanometer period Ru/C multilayers are one of the prime candidates for normal incident reflecting mirrors at wavelengths < 10 nm. Superior performance, which requires uniform layers and smooth interfaces, and high stability of the layered structure under thermal loadings are some of the demands in practical applications. Previous studies however show that the Ru layers in the 2 nm period Ru/C multilayer agglomerate upon moderate annealing, and the layered structure is no longer retained. This agglomeration and crystallization of the Ru layers upon annealing to form almost spherical crystallites is a result of the reduction of surface or interfacial energy from die amorphous high energy non-equilibrium state of the as-prepared sample dirough diffusive arrangements of the atoms. Proposed models for mechanism of thin film agglomeration include one analogous to Rayleigh instability, and grain boundary grooving in polycrystalline films. These models however are not necessarily appropriate to explain for the agglomeration in the sub-nanometer amorphous Ru layers in Ru/C multilayers. The Ru-C phase diagram shows a wide miscible gap, which indicates the preference of phase separation between these two materials and provides an additional driving force for agglomeration. In this paper, we study the evolution of the microstructures and layered structure via in-situ Transmission Electron Microscopy (TEM), and attempt to determine the order of occurence of agglomeration and crystallization in the Ru layers by observing the diffraction patterns.

Domain coarsening by grain boundary migration in ordered Ni4Mo

1986 ◽  
Vol 44 ◽  
pp. 560-561
Author(s):  
K. Vasudevan ◽  
H. P. Kao ◽  
C. R. Brooks ◽  
E. E. Stansbury
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Short Range ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Rapid Cooling ◽  
Temperature Range ◽  
Fee Structure ◽  
Domain Coarsening ◽  
Boundary Reaction

The Ni4Mo alloy has a short-range ordered fee structure (α) above 868°C, but transforms below this temperature to an ordered bet structure (β) by rearrangement of atoms on the fee lattice. The disordered α, retained by rapid cooling, can be ordered by appropriate aging below 868°C. Initially, very fine β domains in six different but crystallographically related variants form and grow in size on further aging. However, in the temperature range 600-775°C, a coarsening reaction begins at the former α grain boundaries and the alloy also coarsens by this mechanism. The purpose of this paper is to report on TEM observations showing the characteristics of this grain boundary reaction.

Ordering in Ni4Mo by TEM and APFIM

1987 ◽  
Vol 45 ◽  
pp. 214-215
Author(s):  
E.A. Kenik ◽  
T.A. Zagula ◽  
M.K. Miller ◽  
J. Bentley
Keyword(s):  
Electron Irradiation ◽  
Low Temperatures ◽  
Short Range ◽  
Atom Probe ◽  
Range Order ◽  
Considerable Time ◽  
Probe Field ◽  
Disordered Phase ◽  
Transmission Electron ◽  
Diffraction Patterns

The state of long-range order (LRO) and short-range order (SRO) in Ni4Mo has been a topic of interest for a considerable time (see Brooks et al.). The SRO is often referred to as 1½0 order from the apparent position of the diffuse maxima in diffraction patterns, which differs from the positions of the LRO (D1a) structure. Various studies have shown that a fully disordered state cannot be retained by quenching, as the atomic arrangements responsible for the 1½0 maxima are present at temperatures above the critical ordering temperature for LRO. Over 20 studies have attempted to identify the atomic arrangements associated with this state of order. A variety of models have been proposed, but no consensus has been reached. It has also been shown that 1 MeV electron irradiation at low temperatures (∼100 K) can produce the disordered phase in Ni4Mo. Transmission electron microscopy (TEM), atom probe field ion microscopy (APFIM), and electron irradiation disordering have been applied in the current study to further the understanding of the ordering processes in Ni4Mo.

Early Education in Short-Range Historical Perspective

1969 ◽  
Vol 14 (8) ◽  
pp. 437-438
Author(s):  
CELIA STENDLER LAVATELLI
Keyword(s):  
Short Range ◽  
Historical Perspective ◽  
Early Education

Short-range order effects in amorphous FexSi1-x/Si multilayers induced by preparation conditions

1998 ◽  
Vol 08 (PR2) ◽  
pp. Pr2-175-Pr2-178 ◽  
Author(s):  
G. T. Pérez ◽  
F. H. Salas ◽  
R. Morales ◽  
L. M. Álvarez-Prado ◽  
J. M. Alameda
Keyword(s):  
Short Range ◽  
Short Range Order ◽  
Range Order ◽  
Order Effects ◽  
Preparation Conditions
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