Tolerance factor, phase stability and order–disorder of the pyrochlore structure

AbstractWe report the synthesis of Sr1-xCaxMnO3 and La0.5Ba0.5MnO3 perovskites over extended cation and oxygen composition ranges and describe the dependence of their phase stability on the tolerance factor t = t(x,T,σ) that is a function of composition, temperature, and oxygen content. We show that magnetic transition temperatures depend strongly on the tolerance factor and charge disorder while dependence on the structural disorder is less important. By reducing charge and structural disorder we have significantly increased the Curie and Neel temperatures for perovskite manganites.

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Perovskite Crystalline Phase Stability Beyond the Goldschmidt Tolerance Factor

10.29363/nanoge.nipho.2020.003 ◽

2019 ◽

Author(s):

Iván Mora-Seró

Keyword(s):

Phase Stability ◽

Crystalline Phase ◽

Tolerance Factor

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Phase stability of intercalated V2O5 battery cathodes elucidated through the Goldschmidt tolerance factor

Physical Chemistry Chemical Physics ◽

10.1039/c9cp00170k ◽

2019 ◽

Vol 21 (15) ◽

pp. 7732-7744

Author(s):

Kit McColl ◽

Furio Corà

Keyword(s):

Structural Stability ◽

Phase Stability ◽

Ionic Mobility ◽

Tolerance Factor ◽

Dispersion Forces

Structural stability, intercalation, layer translation, and ionic mobility investigated in α- and δ-V2O5 using hybrid-exchange DFT, including dispersion forces.

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Tolerance factor and phase stability of the garnet structure

Acta Crystallographica Section C Structural Chemistry ◽

10.1107/s2053229619011975 ◽

2019 ◽

Vol 75 (10) ◽

pp. 1353-1358 ◽

Cited By ~ 9

Author(s):

Zhen Song ◽

Dandan Zhou ◽

Quanlin Liu

Keyword(s):

Phase Stability ◽

High Throughput Screening ◽

Material Design ◽

Tolerance Factor ◽

Screening Methods ◽

Garnet Structure ◽

Garnet Phase ◽

Structural Descriptor ◽

Data Points ◽

The Stability

We introduce a structural descriptor, the tolerance factor, for the prediction and systematic description of the phase stability with the garnet structure. Like the tolerance factor widely adopted for the perovskite structure, it is a compositional parameter derived from the geometrical relationship between multi-type polyhedra in the garnet structure, and the calculation only needs the information of the ionic radius. A survey of the tolerance factor over 130 garnet-type compounds reveals that the data points are scattered in a narrow range. The tolerance factor is helpful in understanding the crystal chemistry of some garnet-type compounds and could serve as a guide for predicting the stability of the garnet phase. The correlation between the tolerance factor and the garnet-phase stability could be utilized by machine learning or high-throughput screening methods in material design and discovery.

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Tolerance Factor and Phase Stability of the Normal Spinel Structure

Crystal Growth & Design ◽

10.1021/acs.cgd.9b01673 ◽

2020 ◽

Vol 20 (3) ◽

pp. 2014-2018 ◽

Cited By ~ 1

Author(s):

Zhen Song ◽

Quanlin Liu

Keyword(s):

Phase Stability ◽

Spinel Structure ◽

Tolerance Factor ◽

Normal Spinel

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Microchemical and crystallographic characterisation of fluorite-based ceramic wasteforms

MRS Proceedings ◽

10.1557/proc-932-55.1 ◽

2006 ◽

Vol 932 ◽

Cited By ~ 4

Author(s):

Martin C. Stennett ◽

Neil C. Hyatt ◽

Ewan R. Maddrell ◽

Fergus G. F. Gibb ◽

Guenter Moebus ◽

...

Keyword(s):

Nuclear Waste ◽

Spectroscopic Analysis ◽

Pyrochlore Structure ◽

Fluorite Structure ◽

Chemical Compositions ◽

Waste Streams ◽

Major Phase ◽

Electron Energy Loss ◽

Quantitative Chemical ◽

Ceramic Matrices

ABSTRACTA number of possible options have been proposed for the encapsulation and immobilisation of long lived actinide (Act) fractions in nuclear waste. Ceramics offer superior durability against chemical migration and the ability to be tailored to accommodate a variety ofdifferent waste streams. Research on the fabrication of dense, durable crystalline matrices for the safe disposal of fissile plutonium is ongoing and this study reports quantitative chemical, structural and spectroscopic analysis on fluorite based host phases.Ceramics based on the fluorite structure are known to be able to incorporate a variety of actinides and in this work two candidate ceramic matrices were investigated: a pyrochlore, Gd2Zr1.60Ce0.20Hf0.20O7; and a zirconolite, (Ca0.90Gd0.10)(Zr0.50Ce0.20Hf0.20Gd0.10)Ti2O7. The chemical compositions of the two major phases observed in the ‘zirconolite’ sample were consistent with the 2M and 4M zirconolite polytypes and the presence of the 4M structure was confirmed by Electron Diffraction (ED). The major phase in the ‘pyrochlore’ ceramic was confirmed by ED to have the pyrochlore structure. Electron Energy Loss Spectroscopy (EELS) data indicated the presence of both Ce3+ and Ce4+ in all the samples.

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Analytical Electron Microscopy of Ion-Implanted Metals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010011831x ◽

1985 ◽

Vol 43 ◽

pp. 282-285

Author(s):

D.I. Potter ◽

M. Ahmed ◽

K. Ruffing

Keyword(s):

Electron Microscopy ◽

Ion Implantation ◽

Friction And Wear ◽

Analytical Electron Microscopy ◽

Chemical Compositions ◽

Surface Chemical ◽

Near Surface ◽

The Past ◽

Analytical Electron ◽

Property Changes

Ion implantation, used extensively for the past decade in fabricating semiconductor devices, now provides a unique means for altering the near-surface chemical compositions and microstructures of metals. These alterations often significantly improve physical properties that depend on the surface of the material; for example, catalysis, corrosion, oxidation, hardness, friction and wear. Frequently the mechanisms causing these beneficial alterations and property changes remain obscure and much of the current research in the area of ion implantation metallurgy is aimed at identifying such mechanisms. Investigators thus confront two immediate questions: To what extent is the chemical composition changed by implantation? What is the resulting microstructure? These two questions can be investigated very fruitfully with analytical electron microscopy (AEM), as described below.

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TEM/AEM characterization of fine-grained clay minerals in very-low-grade rocks: Evaluation of contamination by empa involving celadonite family minerals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100165938 ◽

1996 ◽

Vol 54 ◽

pp. 694-695

Author(s):

Gejing Li ◽

D. R. Peacor ◽

D. S. Coombs ◽

Y. Kawachi

Keyword(s):

Electron Microscopy ◽

Volcanic Rocks ◽

Analytical Electron Microscopy ◽

Metamorphic Rocks ◽

New Mineral ◽

Chemical Compositions ◽

Low Grade ◽

Fine Grained ◽

Depth Analysis ◽

Mineral Aggregates

Recent advances in transmission electron microscopy (TEM) and analytical electron microscopy (AEM) have led to many new insights into the structural and chemical characteristics of very finegrained, optically homogeneous mineral aggregates in sedimentary and very low-grade metamorphic rocks. Chemical compositions obtained by electron microprobe analysis (EMPA) on such materials have been shown by TEM/AEM to result from beam overlap on contaminant phases on a scale below resolution of EMPA, which in turn can lead to errors in interpretation and determination of formation conditions. Here we present an in-depth analysis of the relation between AEM and EMPA data, which leads also to the definition of new mineral phases, and demonstrate the resolution power of AEM relative to EMPA in investigations of very fine-grained mineral aggregates in sedimentary and very low-grade metamorphic rocks.Celadonite, having end-member composition KMgFe3+Si4O10(OH)2, and with minor substitution of Fe2+ for Mg and Al for Fe3+ on octahedral sites, is a fine-grained mica widespread in volcanic rocks and volcaniclastic sediments which have undergone low-temperature alteration in the oceanic crust and in burial metamorphic sequences.

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