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Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 50 for “"fluorite"”.
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Charge carrier relaxation in fluorite-structured oxygen ion conductors /
… that the DRT function of charge carrier in fluorite-structured oxygen ion conductive ceramics and single crystals may be described nearly Gaussian-shaped curve in logarithmic time scale, which narrows with increasing temperature and decreasing dopant concentration.
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The production of fluorite crystals in the electric furnace
Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Electrochemical Engineering, 1926.
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Paramagnetic resonance of transition group ions in crystals with the fluorite structure
The electronic paramagnetic resonance of Co2+ in cubic sites of CaF2 and in trigonal sites of CdF2 have been observed at a frequency of 9 GHz and at liquid helium temperature. The trigonal spectra have an axial symmetry about a (lll) direction with g11 = 2.25 +/- 0.05 and g1 = 4.45 +/- 0.10. The …
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Tailoring Perovskite- and Fluorite-Type Oxides for Solid Oxide Fuel Cells (SOFCs)
… The objective of thesis is to develop and tune fluorite- and perovskite-type metal oxides that serve as alternate anodes, electrolytes, and cathodes for intermediate temperature SOFCs. Here, the chemical reactivity between a fluorite-based Ce0.7RE0.2Mo0.1O2 (RE = Y, Sm) anode and 8 mol% …
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Solid transformations and premelting phenomena in fluorite structures and the system SrCl₂BaCl₂
… undergoes the transformation from the cubic fluorite to a hexagonal structure in the temperature range 660°-750°C, with nucleation and grain growth. BaCl<sub>2</sub> occurs in three forms: cubic, orthorhombic, and hexagonal. The cubic form is stable below about 165°C and transforms …
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The Chemistry and Crystallography of Doped Bixbyite, Braunite and Novel Anion-Deficient Fluorite Oxides
… The bixbyite and many related defective fluorite structures have received an increasing amount of attention for at least the last decade for their application as semiconductors, optoelectronics, superconductivity, magnetism, and catalysis. The bixbyite structure has deep historical roots …
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The Effect of Hydrostatic Pressure on The Ionic Conductivity of Some Crystals With The Fluorite Structure
The effect of hydrostatic pressure on the ionic conductivity of CaF(,2), SrF(,2), BaF(,2), CdF(,2, )SrC(, 2), PbF(,2), PbC (,2), PbBr(,2) and PbI(,2) has been studied for pressures up to 0.6 GPa and temperatures up to near the melting point. The activation volumes for extrinsic vacancy motion were …
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Low temperature aqueous solubility of fluorite at temperatures of 5, 25, and 50°C and ionic strengths up to 0.72M
Historical fluorite solubility research found that fluorite solubilities varied over three orders-of-magnitude and appear to be inconsistent with several recently determined fluorite solubilities. This research involved a comprehensive series of solubility experiments run over a period of three …
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Magmatic-hydrothermal critical ore systems: identifying fluid sources and tracing fluid evolution
… second study of this dissertation tested whether fluorite records the REE composition of its source. Fluorite was synthesized from REE-bearing solutions from 25–150 °C. Fluorite REE patterns are consistent with the parent solution under all tested conditions. Application to the Baiyanghe deposit …
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Synthesis and characterisation of d-Bi2O3 related materials stabilised by substitutions of Ca, Ga, Nb and Re.
… impedance spectroscopy. The structure of two new fluorite-related materials, Bi\(_6\)Ca\(_3\)ReO\(_{15.5}\) and Bi\(_{10}\)Ca\(_5\)ReO\(_{23.5}\), were studied. Bi\(_6\)Ca\(_3\)ReO\(_{15.5}\) formed a face-centred cubic fluorite-related structure and Bi\(_{10}\)Ca\(_5\)ReO\(_{23.5}\) a …
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The geochemistry of carbonate-hosted Pb-Zn-Ag mineralization in the Lavrion District, Attica, Greece: fluid inclusion, stable isotope, and rare earth element studies
… abundant late in the paragenetic sequence with fluorite and barite. Fluid inclusion studies of sphalerite, fluorite, calcite, and quartz in carbonate-replacement deposits suggest that they were deposited in thermal pulses (132°-365°C) from CO2-poor, low- to moderately-saline (1 to 20 wt% NaCl …
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Crystallographic origins of fast-ion conduction in pyrochlore
… A2B2O7, a superstructure of (A,B)20 3.5 defect fluorite-like array. These materials have technological promise for use in electrochemical devices such as oxygen sensors and solid-oxide fuel-cells. The pathway for ion conduction proposed by several authors has been a jump between equivalent …
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Fundamental studies on ionomer glasses
… a two stage crystallization of calcium fluoride (fluorite) and anorthite. The anorthite phase crystallized from fluorite nuclei and, in effect, crystallization occurred by a bulk nucleation mechanism. The glass will also undergo significant crystallization to fluorite below the glass transition …
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Grain boundary chemistry and morphology of heavily doped cerium dioxide
… for oxygen ion conducting ceramics of the cubic fluorite structure, in which grain boundaries are known to limit the overall ionic conductivity of polycrystals. Measurements of grain boundary segregation of the aliovalent dopants Gd3+ and Ta5+ in heavily doped ceria have been made using a Vacuum …
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Fluid inclusion and trace element studies of the gem pegmatites of Mt. Antero, Colorado
… clear and milky quartz, phenakite, muscovite, fluorite, garnet, pyrite, topaz and calcite. Aquamarine and smoky quartz contain abundant primary fluid inclusions outlining growth zones, as well as numerous trails of pseudosecondary and secondary inclusions. Salinities and homogenization …
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Petrology and geochemistry of precious and base metal mineralization, North Amethyst vein system Mineral County, Colorado
… calcite, sericite, chlorite, hematite, adularia, fluorite, base metal sulfides, and Ag-tetrahedrite. The first association (fluid boiling at >350°C to 270°C, <2 wt% HaCl equiv.) has a calculated depth of >1000m; the second association (nonboiling, basemetal assemblages: 280°C to 220°C, 5-11 wt%; …
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Formation and growth of irradiation-induced defect structures in ceria
… of the radiation damage process in the common fluorite-type ceramic oxide fuel, ceria (CeO2) was selected as a surrogate material of UO2 for this study. According to previous studies, ceramic materials with a fluorite crystal structure possess high radiation tolerance. Using CeO2 single …
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Distribution and causes of high fluoride groundwater in the western Bushveld area of South Africa
… of fluorine-bearing minerals, principally fluorite, mica, amphibole and apatite, and that high F- groundwater would be hosted in rocks with a high fluorine (F) content. It was further hypothesised . that groundwater residence time, rare F-bearing minerals, ion exchange reactions and …
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Preparation and characterization of praseodymium oxide films and powders.
… for 1-3 hours. X-ray diffraction revealed the fluorite structure of Pr6O11 and the crystallite size was calculated. X-ray photoelectron spectroscopy was employed to study the composition of the oxide films and also the oxidation state of Pr. Scanning electron microscopy was utilized to study …
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Stratigraphy and petrography of the Wytheville formation in southwest Virginia
… of chert and minor but conspicuous quantities of fluorite also occur in the formation. In thin section at least nine lithologies are discernible, including both equigranular and inequigranular dolomites, calcitic dolomites, magnesian limestones, micrites, pelsparites, siliceous dolomites, and …
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