151Eu Mössbauer spectroscopic and XRD study on some fluorite-type solid solution systems, EuyM1−yO2−y/2 (M=Zr, Hf, Ce)

A detailed transmission electron microscope and X-ray powder diffraction study has been made of the so-called 'defect fluorite' phase field in the ZrO2-PrO1.5 system and of its close relationship to the pyrochlore solid solution field in the same system. Even for the lowest possible PrO1.5 content within the 'defect fluorite' phase field, it is clear that the sharp Bragg reflections characteristic of the underlying fluorite average structure are accompanied by some of the 'satellite reflections' characteristic of the pyrochlore solid solution field. As the PrO1.5 content increases, these satellite reflections increase systematically in intensity as well as sharpening very considerably. It is shown that this 'defect fluorite' phase field cannot be adequately described either in terms of random point defects within an average fluorite-type matrix or in terms of a diphasic texture of pyrochlore domains embedded coherently into a fluorite matrix, but must be regarded as enuinely intermediate between these two end-member structures and of commensurately modulated fluorite type. A group theoretical approach is used to propose a model for the structural deviation from the underlying fluorite average structure.

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Synthesis and characterization of mixed fluorides with PbF2 and ScF3

Powder Diffraction ◽

10.1154/1.1948391 ◽

2005 ◽

Vol 20 (3) ◽

pp. 254-258 ◽

Cited By ~ 1

Author(s):

S. N. Achary ◽

A. K. Tyagi

Keyword(s):

Solid Solution ◽

Phase Equilibria ◽

Room Temperature ◽

Unit Cell Volume ◽

Solubility Limit ◽

Synthesis And Characterization ◽

Temperature Phase ◽

Fluorite Type ◽

Low Temperature Phase

A series of mixed fluoride compositions with PbF2 and ScF3 were prepared by heating the intimate mixtures of component fluorides at 600 °C for 10 h followed by slowly cooling to room temperature. The products obtained were analyzed by powder XRD to reveal the phases present in them and hence the low-temperature phase equilibria in the PbF2-ScF3 system. The phase equilibria show the fluorite-type solid solution up to the composition of about 15 mol% of ScF3 in the PbF2 lattice. The unit cell volume decreases with increasing ScF3 contents in the fluorite-type solid solutions. Beyond the solubility limit, the biphasic mixture of the cubic fluorite-type solid solution and leftover ScF3 is found to exist.

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Ionic Conductivity of the new Fluoride-Ion Conductor Casn2F6

MRS Proceedings ◽

10.1557/proc-756-ee3.5 ◽

2002 ◽

Vol 756 ◽

Author(s):

Michael F. Bell ◽

Georges DéNés ◽

Zhimeng Zhu

Keyword(s):

Solid Solution ◽

Complex Impedance ◽

Crystalline Material ◽

Mixed Conductor ◽

Impedance Method ◽

Fluoride Ion ◽

Ion Conductor ◽

Covalently Bonded ◽

Fluorite Type ◽

First Time

ABSTRACTMetastable CaSn2F6 has been prepared for the first time and characterized. It is a well crystalline material that leaches SnF2 in water to give the microcrystalline fluorite-type Ca1-xSnxF2 solid solution. In both materials, tin(II) is covalently bonded to fluorine, and thus carries a stereoactive non-bonding electronic pair. The electrical conductivity of CaSn2F6 was measured by the complex impedance method. The CaSn2F6 material was found to be a mixed conductor (τi = 0.50), with a F- conductivity a little below that of α-SnF2. On heating to 250°C, it decomposes irreversibly to give SnF2 and probably amorphous CaF2 (undetected).

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Phase transitions induced by solid solution in stuffed derivatives of quartz: A powder synchrotron XRD study of the LiAlSiO4-SiO2join

American Mineralogist ◽

10.2138/am-2000-0711 ◽

2000 ◽

Vol 85 (7-8) ◽

pp. 971-979 ◽

Cited By ~ 21

Author(s):

Hongwu Xu ◽

Peter J. Heaney ◽

George H. Beall

Keyword(s):

Solid Solution ◽

Phase Transitions ◽

Xrd Study ◽

Derivatives Of ◽

Synchrotron Xrd

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Hydrogen Ordering and Metal-Semiconductor Transitions in Rare-Earth Hydrides

MRS Proceedings ◽

10.1557/proc-1122-o01-04 ◽

2008 ◽

Vol 1122 ◽

Author(s):

P. Vajda

Keyword(s):

Phase Diagram ◽

Solid Solution ◽

Magnetic Properties ◽

Electronic Structure ◽

Rare Earth ◽

Fluorite Type ◽

The Rare Earth

AbstractAfter an introduction to the rare earth – hydrogen phase diagram, stressing the often broad existence range of the solid solution (α), dihydride (β) and trihydride (γ) phases, we are describing in detail the fluorite-type dihydride and its superstoichiometric composition, RH2+x, where the x atoms occupy the available octahedral interstitial sites. It is shown how these additional x atoms interact with each other to form ordered H superlattices (sometimes distorting the cubic CaF2 structure) and how the latter influences the electronic structure of the systems modifying the magnetic properties and/or leading to metal-semiconductor transitions.

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Crystallization of Fluorite-Type Solid Solution from Alkoxides in the System Y2O3-TiO2

Journal of the American Ceramic Society ◽

10.1111/j.1151-2916.1986.tb04824.x ◽

1986 ◽

Vol 69 (8) ◽

pp. C-166-C-167 ◽

Cited By ~ 2

Author(s):

Osamu Yamaguchi ◽

Akira Narai ◽

Hideki Kudara ◽

Kiyoshi Shimizu

Keyword(s):

Solid Solution ◽

Fluorite Type

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Powder XRD study of Ba4Eu3F17: A new anion rich fluorite related mixed fluoride

Powder Diffraction ◽

10.1154/1.1477198 ◽

2002 ◽

Vol 17 (3) ◽

pp. 225-229 ◽

Cited By ~ 3

Author(s):

S. N. Achary ◽

S. J. Patwe ◽

A. K. Tyagi

Keyword(s):

Powder Diffraction ◽

Diffraction Data ◽

Title Compound ◽

Salient Feature ◽

Powder Diffraction Data ◽

Fluoride Ions ◽

Static Vacuum ◽

Xrd Study ◽

Fluorite Type ◽

Starting Model

The compound Ba4Eu3F17 was prepared by heating pre-dried BaF2 and EuF3 (4:3) at 800 °C for 8 h in static vacuum. The colorless polycrystalline product obtained was characterized by Rietveld refinement of the observed powder diffraction data with a starting model of Ba4Y3F17. The title compound Ba4Eu3F17 crystallizes in rhombohedral lattice with lattice parameters, a=11.1787(4) and c=20.5789(10) Å, Z=3 (Space group R 3, No. 148). The Ba4Eu3F17 structure can be described as an ordered anion-rich fluorite type structure with the formation of Eu6F37 clusters. There are two crystallographically distinct Ba (CN=10, 11) and one distinct Eu (CN=8). The typical Ba(1)–F, Ba(2)–F, and Eu–F bond lengths range from 2.56 to 2.83 Å, 2.54 to 3.25 Å, and 2.24 to 2.49 Å, respectively. The salient feature of the structure is that the EuF8 polyhedra share their corner to form a cubo-octahedron of fluoride ions. The cubic BaF8 polyhedra of BaF2 are modified to Ba(1)–F10 and Ba(2)–F11 polyhedra in this structure. The cubo-octahedron encloses extra fluorine F(8) inside it.

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