Structural Effect of Pu Substitutions on the Zr-Site in Zirconolite

2000 ◽  
Vol 663 ◽  
Author(s):  
B.D. Begg ◽  
R.A. Day ◽  
A. Brownscombe
Keyword(s):  
Solid Solution ◽  
Pyrochlore Structure ◽  
Structural Effect ◽  
Structural Transitions ◽  
Compositional Range ◽  
Ionic Size ◽  
The Stability

ABSTRACTAs the level of Pu4+ substituted on the Zr-site in CaZr1-xPuxTi2O7 zirconolite increased, from x=0.1 to 0.6, a series of structural transitions occurred from zirconolite-2M to zirconolite-4M and subsequently from zirconolite-4M to pyrochlore. The solid-solution limit for Pu4+ substituted on the Zr-site in zirconolite-2M was ~ 0.15 formula units. Zirconolite-4M was only stable over a narrow compositional range, centered about CaZr0.59Pu0.41Ti2O7, whilst the pyrochlore structure was stabilized with CaZr0.4Pu0.6Ti2O7 stoichiometry. The stability of the zirconolite polytypes is therefore sensitive to the average effective ionic size of the ions occupying the seven-coordinated Zr-site. The reduction in Pu from Pu4+ to Pu3+ destabilized the zirconolite-4M, producing a mixture of perovskite and possibly zirconolite-3T. The CaZr0.4Pu0.6Ti2O7 pyrochlore was also predominantly transformed to perovskite as a result of this reduction of Pu.

Defect fluorite structures containing Bi 2 O 3 : the system Bi 2 O 3 -Nb 2 O 5

1986 ◽  
Vol 406 (1831) ◽  
pp. 173-182 ◽  
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
High Resolution ◽  
Electron Diffraction ◽  
Pyrochlore Structure ◽  
High Resolution Electron Microscopy ◽  
Unit Cell ◽  
Compositional Range ◽  
Resolution Electron ◽  
Structural Principles

A previously described solid solution in the system Bi 2 O 3 -Nb 2 O 5 based on the δ-Bi 2 O 3 structure has been reinvestigated by electron diffraction and high resolution electron microscopy. Four distinct phases have been found, all of which are based upon defect fluorite structures, and the structural principles of the phase with the greatest compositional range have been elucidated. This involves an adaption of elements of the pyrochlore structure with an ordering of niobium-oxygen octahedra into groups lying on the {111} planes of an enlarged cubic unit cell, separated by a matrix of δ-Bi 2 O 3 structure.

Pyrochlores. II. An investigation of La2Ce2O7 by neutron diffraction

1967 ◽  
Vol 45 (6) ◽  
pp. 609-614 ◽  
Author(s):  
François Brisse ◽  
Osvald Knop
Keyword(s):  
Pyrochlore Structure ◽  
Lattice Parameter ◽  
Neutron Powder Diffraction ◽  
Short Range Ordering ◽  
Pyrochlore Type ◽  
Ionic Size ◽  
The Stability ◽  
Stability Limits ◽  
Neutron Powder Diffraction Pattern ◽  
Degree Of Order

The lattice parameter of La2Ce2O7 fired at 1 400 °C was found to be 5.5700 ± 7 Å (at 20 ± 2 °C). Its crystal structure was of the disordered fluorite rather than the pyrochlore type. The degree of order in the structure could not be established from the neutron powder diffraction pattern, but it is likely that the metal and oxygen atoms were distributed at random, possibly with some tendency to short-range ordering. It would appear that for Ce4+ the ionic size requirements for the formation of the pyrochlore structure are no longer satisfied, and that the cerates M23+Ce24+O7 are outside the stability limits for 3–4 pyrochlores.

A review on phase prediction in high entropy alloys

2021 ◽  
pp. 095440622110089
Author(s):  
Vinay Kumar Soni ◽  
S Sanyal ◽  
K Raja Rao ◽  
Sudip K Sinha
Keyword(s):  
Solid Solution ◽  
Phase Formation ◽  
Single Phase ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
Modeling Tools ◽  
High Entropy ◽  
Recent Developments ◽  
Phase Prediction ◽  
The Stability

The formation of single phase solid solution in High Entropy Alloys (HEAs) is essential for the properties of the alloys therefore, numerous approach were proposed by many researchers to predict the stability of single phase solid solution in High Entropy Alloy. The present review examines some of the recent developments while using computational intelligence techniques such as parametric approach, CALPHAD, Machine Learning etc. for prediction of various phase formation in multicomponent high entropy alloys. A detail study of this data-driven approaches pertaining to the understanding of structural and phase formation behaviour of a new class of compositionally complex alloys is done in the present investigation. The advantages and drawbacks of the various computational are also discussed. Finally, this review aims at understanding several computational modeling tools complying the thermodynamic criteria for phase formation of novel HEAs which could possibly deliver superior mechanical properties keeping an aim at advanced engineering applications.

Electron Structure and Piezoelectric Characteristics of PMZN System Piezoceramics

2007 ◽  
Vol 280-283 ◽  
pp. 185-188 ◽  
Author(s):  
Jing Zhou ◽  
Wen Chen ◽  
Hua Jun Sun ◽  
Qing Xu
Keyword(s):  
Ferroelectric Phase ◽  
Pyrochlore Structure ◽  
Covalent Bond ◽  
Axial Direction ◽  
Electron Structure ◽  
System Structure ◽  
Necessary Condition ◽  
Total System ◽  
The Stability ◽  
Piezoelectric Characteristics

The electron structure of Pb(Zr1/2Ti1/2)O3(PZT), Pb(Zn1/3Nb2/3)O3(PZN) and Pb(Mn1/3Sb2/3)O3 (PMS) systems was calculated by the SCF-DV-Xα calculation method. The effects of ABO3-type perovskite and pyrochlore ceramic electron structure on their piezoelectricity were also studied. The results showed that the ferroelectric phase is more stable than paraelectric phase and the necessary condition of stable existing ferroelectric is the mixed orbit of O2p orbit and the out layer d orbit of B-site atom. The stability of ferroelectricity can be indicated by the strength of mixed orbit. When (Zr, Ti) was substituted by Mn1/3Sb2/3, Zn1/3Nb2/3, if it could form tetragonal perovskite structure, the total system energy would reduce and the mixed orbit will enhance, which improves the ferroelectricity of PZT system. However, if it forms a cubic pyrochlore structure, the ferroelectricity would lose because the covalent bond strength of B-O (axial direction) and B-O (vertical axial direction) is different obviously, which lead to the system structure become unstable.

Influence of Quenching Parameters on the Stability of the β Solid Solution in a High-Strength Titanium Alloy

2019 ◽  
Vol 120 (5) ◽  
pp. 476-482
Author(s):  
A. G. Illarionov ◽  
I. V. Narygina ◽  
S. M. Illarionova ◽  
M. S. Karabanalov
Keyword(s):  
Solid Solution ◽  
Titanium Alloy ◽  
High Strength ◽  
The Stability

scholarly journals On the Issue of Radiation-Induced Instability in Binary Solid Solutions

2014 ◽  
Vol 2014 ◽  
pp. 1-5
Author(s):  
Santosh Dubey ◽  
S. K. Joshi ◽  
B. S. Tewari
Keyword(s):  
Solid Solution ◽  
Stability Analysis ◽  
Reaction Diffusion ◽  
Reaction Diffusion Equations ◽  
Diffusion Equations ◽  
Control Parameters ◽  
Binary Solid Solution ◽  
Nonlinear Reaction ◽  
Radiation Induced ◽  
The Stability

The stability of a binary solid solution under irradiation has been studied. This has been done by performing linear stability analysis of a set of nonlinear reaction-diffusion equations under uniform irradiation. Owing to the complexity of the resulting system of eigenvalue equations, a numerical solution has been attempted to calculate the dispersion relations. The set of reaction-diffusion equations represent the coupled dynamics of vacancies, dumbbell-type interstitials, and lattice atoms. For a miscible system (Cu-Au) under uniform irradiation, the initiation and growth of the instability have been studied as a function of various control parameters.

scholarly journals Synthesis and Electrochemical Performance of Graphene Wrapped SnxTi1−xO2Nanoparticles as an Anode Material for Li-Ion Batteries

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Xing Xin ◽  
Xufeng Zhou ◽  
Tao Shen ◽  
Zhaoping Liu
Keyword(s):  
Solid Solution ◽  
Electrochemical Performance ◽  
Anode Material ◽  
Solution Method ◽  
Substitutional Solid Solution ◽  
Li Ion Batteries ◽  
Li Ion ◽  
The Stability ◽  
Ti Content ◽  
Aqueous Solution Method

Ever-growing development of Li-ion battery has urged the exploitation of new materials as electrodes. Here,SnxTi1-xO2solid-solution nanomaterials were prepared by aqueous solution method. The morphology, structures, and electrochemical performance ofSnxTi1-xO2nanoparticles were systematically investigated. The results indicate that Ti atom can replace the Sn atom to enter the lattice of SnO2to form substitutional solid-solution compounds. The capacity of the solid solution decreases while the stability is improved with the increasing of the Ti content. Solid solution withxof 0.7 exhibits the optimal electrochemical performance. The Sn0.7Ti0.3O2was further modified by highly conductive graphene to enhance its relatively low electrical conductivity. The Sn0.7Ti0.3O2/graphene composite exhibits much improved rate performance, indicating that theSnxTi1-xO2solid solution can be used as a potential anode material for Li-ion batteries.

Fabrication and Stability of CoAl2O4 Ceramic Pigment for 3D Printing

2017 ◽  
Vol 898 ◽  
pp. 1935-1939 ◽  
Author(s):  
Yuan Song ◽  
Yuan Lin Zheng ◽  
Yu Fei Tang ◽  
Hai Bing Yang
Keyword(s):  
Solid Solution ◽  
Aqueous Solution ◽  
3D Printing ◽  
Zeta Potential ◽  
Spinel Structure ◽  
Sol Gel ◽  
Ceramic Pigment ◽  
Ceramic Pigments ◽  
Oxide Solid Solution ◽  
The Stability

Ceramic pigment is the key component of the ink color in the 3D printing process of ceramic products. The color performance and stability of ceramic pigments after calcination still need to be improved. In the present study the cobalt aluminate (CoAl2O4) ceramic pigment powders were fabricated by sol-gel method. The effects of fabrication processes on color properties of CoAl2O4 ceramic pigments were investigated. The compositions and morphologies of CoAl2O4 ceramic pigment powders were characterized. The stability of CoAl2O4 ceramic pigments was discussed. The results showed that the CoAl2O4 ceramic pigment with high chroma was obtained at calcination temperature of 1200°C and the Co/Al ratio is 1:3. The Zeta potential of the fabricated CoAl2O4 ceramic pigment powders in aqueous solution was-66.2 mV, which represented good dispersion stability. The chroma and saturation of the CoAl2O4 ceramic pigment increased owing to that the oxide solid solution in the spinel structure increased after being sintered at 1300 oC.

An EXAFS study of cation site distortions through the P2/c-P1̄ phase transition in the synthetic cuproscheelite-sanmartinite solid solution

1994 ◽  
Vol 58 (391) ◽  
pp. 185-199 ◽  
Author(s):  
P. F. Schofield ◽  
J. M. Charnock ◽  
G. Cressey ◽  
C. M. B. Henderson
Keyword(s):  
Phase Transition ◽  
Solid Solution ◽  
Stability Field ◽  
Cation Site ◽  
Cu Content ◽  
Square Planar ◽  
Jahn Teller ◽  
Exafs Study ◽  
Four Square ◽  
The Stability

AbstractEXAFS spectroscopy has been used to monitor changes in divalent cation site geometries across the P2/c-P1̄ phase transition in the sanmartinite (ZnWO4)-cuproscheelite (CuWO4) solid solution at ambient and liquid nitrogen temperatures. In the ZnWO4 end member, Zn occupies axially-compressed ZnO6 octahedra with two axial Zn-O bonds at approximately 1.95 Å and four square planar Zn-O bonds at approximately 2.11 Å. The substitution of Zn by Cu generates a second Zn environment with four short square planar Zn-O bonds and two longer axial Zn-O bonds. The proportion of the latter site increases progressively as the Cu content increases. Cu EXAFS reveals that the CuO6 octahedra maintain their Jahn-Teller axially-elongate geometry throughout the majority of the solid solution and only occur as axially-compressed octahedra well within the stability field of the Zn-rich phase with monoclinic long-range order.

Crystal Chemistry and Phase Equilibria of the BaO-R2O3-CuO Systems

1989 ◽  
Vol 33 ◽  
pp. 453-465 ◽  
Author(s):  
Winnie Wong-Ng ◽  
Boris Paretzkin ◽  
Edwin R. Fuller
Keyword(s):  
Solid Solution ◽  
Ternary Phase ◽  
Systematic Investigation ◽  
Size Factor ◽  
Compound Formation ◽  
Solid Solution Formation ◽  
Solution Formation ◽  
Phase Compatibility ◽  
The Stability ◽  
Phase Relationships

AbstractTwo important factors, the progressively decreasing size of the lanthanides, which is known as the lanthanide contraction, as well as the stability of different oxidation states of these elements influence the prediction of compound formation in the Ba-R-Cu-O systems. A systematic investigation of these lanthanide systems and comparison with the Y system has revealed a correlation of the effect of the above factors, in particular the size factor, on the trend of phase formation, solid solution formation and phase compatibility diagrams of the Ba-R-Cu-O systems. For example, it has been found that the smaller the size of R3+ or the greater the mismatch betwaen Ba2+ and R3+ in the solid solution series Ba2-ZR1+lCu3O6+x, the smaller the extent of solid solution formation. This differing extent of solid solution formation influences the ternary phase relationships.

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