The Experts below are selected from a list of 219 Experts worldwide ranked by ideXlab platform
M I Arriortua - One of the best experts on this subject based on the ideXlab platform.
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synthesis of new ln4 al2o6f2 o2 ln sm eu gd phases with a Cuspidine related structure
IUCrJ, 2019Co-Authors: Aroa Moranruiz, P R Slater, Aritza Wainmartin, Alodia Orera, M L Sanjuan, Aitor Larranaga, M I ArriortuaAbstract:The first fluorination of the Cuspidine-related phases of Ln4(Al2O7□)O2 (where Ln = Sm, Eu, Gd) is reported. A low-temperature reaction with poly(vinylidene difluoride) lead to the fluorine being substituted in place of oxygen and inserted into the vacant position between the dialuminate groups. X-ray photoelectron spectroscopy shows the presence of the F 1s photoelectron together with an increase in Al 2p and rare-earth 4d binding energies supporting F incorporation. Energy-dispersive X-ray spectroscopy analyses are consistent with the formula Ln4(Al2O6F2)O2, confirming that substitution of one oxygen by two fluoride atoms has been achieved. Rietveld refinements show an expansion in the cell upon fluorination and confirm that the incorporation of fluoride in the Ln4(Al2O7□)O2 structure results in changes in Al coordination from four to five. Thus, the isolated tetrahedral dialuminate Al2O7 groups are converted to chains of distorted square-based pyramids. These structural results are also discussed based on Raman spectra.
P R Slater - One of the best experts on this subject based on the ideXlab platform.
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synthesis of new ln4 al2o6f2 o2 ln sm eu gd phases with a Cuspidine related structure
IUCrJ, 2019Co-Authors: Aroa Moranruiz, P R Slater, Aritza Wainmartin, Alodia Orera, M L Sanjuan, Aitor Larranaga, M I ArriortuaAbstract:The first fluorination of the Cuspidine-related phases of Ln4(Al2O7□)O2 (where Ln = Sm, Eu, Gd) is reported. A low-temperature reaction with poly(vinylidene difluoride) lead to the fluorine being substituted in place of oxygen and inserted into the vacant position between the dialuminate groups. X-ray photoelectron spectroscopy shows the presence of the F 1s photoelectron together with an increase in Al 2p and rare-earth 4d binding energies supporting F incorporation. Energy-dispersive X-ray spectroscopy analyses are consistent with the formula Ln4(Al2O6F2)O2, confirming that substitution of one oxygen by two fluoride atoms has been achieved. Rietveld refinements show an expansion in the cell upon fluorination and confirm that the incorporation of fluoride in the Ln4(Al2O7□)O2 structure results in changes in Al coordination from four to five. Thus, the isolated tetrahedral dialuminate Al2O7 groups are converted to chains of distorted square-based pyramids. These structural results are also discussed based on Raman spectra.
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a computational study of oxide ion migration and water incorporation in the Cuspidine system la4 ti2o8 o2
Solid State Ionics, 2008Co-Authors: Emma Kendrick, Mike Russ, P R SlaterAbstract:The Cuspidine system, La4(Ti2-xGaxO8-x/2)O2 has recently been shown to display significant oxide ion conductivity at elevated temperatures, with evidence for proton conduction at low temperatures in wet atmospheres. In this paper we present a computer modelling study of the La4(Ti2O8)O2 (x=0) end-member. In agreement with experimental studies, the most favourable oxide ion vacancy defect is found at the bridging oxygen position (O3). Oxide ion migration is shown to proceed via a cooperative vacancy migration process with a calculated activation energy of 1.51 eV, in very good agreement with experiment. The computational results for water incorporation suggest that oxygen vacancies are required for water incorporation to occur, which also agrees with experiment, and the most favourable position for the proton is the bridging oxygen (O3).
Aroa Moranruiz - One of the best experts on this subject based on the ideXlab platform.
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synthesis of new ln4 al2o6f2 o2 ln sm eu gd phases with a Cuspidine related structure
IUCrJ, 2019Co-Authors: Aroa Moranruiz, P R Slater, Aritza Wainmartin, Alodia Orera, M L Sanjuan, Aitor Larranaga, M I ArriortuaAbstract:The first fluorination of the Cuspidine-related phases of Ln4(Al2O7□)O2 (where Ln = Sm, Eu, Gd) is reported. A low-temperature reaction with poly(vinylidene difluoride) lead to the fluorine being substituted in place of oxygen and inserted into the vacant position between the dialuminate groups. X-ray photoelectron spectroscopy shows the presence of the F 1s photoelectron together with an increase in Al 2p and rare-earth 4d binding energies supporting F incorporation. Energy-dispersive X-ray spectroscopy analyses are consistent with the formula Ln4(Al2O6F2)O2, confirming that substitution of one oxygen by two fluoride atoms has been achieved. Rietveld refinements show an expansion in the cell upon fluorination and confirm that the incorporation of fluoride in the Ln4(Al2O7□)O2 structure results in changes in Al coordination from four to five. Thus, the isolated tetrahedral dialuminate Al2O7 groups are converted to chains of distorted square-based pyramids. These structural results are also discussed based on Raman spectra.
Roger H Mitchell - One of the best experts on this subject based on the ideXlab platform.
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Cuspidine sodalite natrocarbonatite from oldoinyo lengai tanzania a novel hybrid carbonatite formed by assimilation of ijolite
Mineralogical Magazine, 2008Co-Authors: Roger H Mitchell, F A BeltonAbstract:A unique hybrid natrocarbonatite, collected from the new ash cone of the volcano Oldoinyo Lengai, Tanzania in July 2008, consists of phenocrysts of nyerereite and gregoryite together with xenocrysts of clinopyroxene, nepheline and Ti-andradite set in a groundmass of Cuspidine, sodalite, ferroan manganoan monticellite, K-Fe sulphide and manganoan titanian magnetite and gregoryite. The xenocrysts were not in equilibrium with the melt which formed their current host, as clinopyroxenes and Ti-andradite are mantled by Cuspidine, and nepheline by sodalite and phlogopite-potassian kinoshitalite solid solutions. A microxenolith of ijolite exhibits similar reaction phenomena. The minerals of the xenocryst suite have similar compositions to plutonic ijolites found at Oldoinyo Lengai, and are thus considered to be derived by the fragmentation of such material in a previously contaminated natrocarbonatite melt. The latter, which has Cuspidine, sodalite and monticellite as primary liquidus phases, is considered to have been formed by the complete assimilation of ijolitic material in a natrocarbonatite magma at depth in the volcano conduit. The occurrence of trace amounts of Cuspidine, Fe-Mn-monticellite, K-Fe sulphide and Mn-Ti-spinel in recently erupted natrocarbonatites is ascribed to similar, but less extensive, assimilation of silicate material prior to their eruption.
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marianoite a new member of the Cuspidine group from the prairie lake silicocarbonatite ontario
Canadian Mineralogist, 2008Co-Authors: Anton R Chakhmouradian, Roger H Mitchell, Peter C Burns, Yulia Mikhailova, Ekaterina P ReguirAbstract:Marianoite, a new member of the Cuspidine group of minerals, occurs in phlogopite–calcite silicocarbonatite in the western part of the Mesoproterozoic Prairie Lake intrusive complex, in northwestern Ontario, Canada. The mineral forms flattened prismatic crystals with resorbed faces, up to 0.3 mm in length, and is associated with uranoan pyrochlore, titanite and natrolite–muscovite pseudomorphs after xenocrystic nepheline. The crystals are translucent, very pale yellow macroscopically and colorless in plane-polarized light. The mineral is biaxial negative (α 1.700, β 1.715, γ 1.725, 2 V meas 80°, 2 V calc 78°) and shows a weak optic-axis dispersion ( r v ). Marianoite is relatively homogeneous in composition; its average empirical formula is Na 1.93 (Ca 4.00 Mn 0.04 ) ∑4.04 (Nb 0.97 Zr 0.90 Ti 0.09 Fe 0.08 Mg 0.03 Hf 0.01 ) ∑2.08 (Si 3.97 O 14 )O 2.93 F 1.07 . By analogy with wohlerite, the simplified formula of marianoite should be written Na 2 Ca 4 (Nb,Zr) 2 (Si 2 O 7 ) 2 (O,F) 4 . The structure of the new mineral species, refined by single-crystal methods to an R 1 of 4.65% (for | F o | > 4σ F ), is monoclinic, space group P 2 1 ; the unit-cell parameters are: a 10.8459(15) A, b 10.2260(14) A, c 7.2727(10) A, β 109.332(3)°, V 761.1(3) A 3 ( D calc 3.45 g/cm 3 ). The mineral is isostructural with wohlerite [Na 2 Ca 4 (Zr,Nb) 2 (Si 2 O 7 ) 2 (O,F) 4 ], but shows the preponderance of Nb in the smallest octahedrally coordinated cation sites in its crystal structure. The occupancy of these sites cannot be determined accurately because of the similar X-ray scattering characteristics and ionic radii of Nb 5+ and Zr 4+ . The mineral is named in honor of Anthony Nicola Mariano (b. 1930), in recognition of his contributions to the study of alkaline rocks and carbonatites.
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niocalite Cuspidine solid solution and manganoan monticellite from natrocarbonatite oldoinyo lengai tanzania
Mineralogical Magazine, 2004Co-Authors: Roger H Mitchell, F BeltonAbstract:Lapilli and spatter of natrocarbonatite extruded from the T56B cone of Oldoinyo Lengai (Tanzania) in August 2003 are unusually rich in apatite, silicate, oxide and sulphide minerals. These minerals occur primarily within inclusions of quenched natrocarbonatite in gregoryite and fractures in nyerereite-gregoryite intergrowths. Silicates include members of the sodian Cuspidine–niobian Cuspidine–niocalite solid-solution series and manganoan monticellite. Oxides are represented by members of the magnesioferrite–jacobsite–magnetite solid-solution series. Sulphides occurring in decreasing order of abundance include: ferroan alabandite, manganoan ferroan sphalerite, galena and pyrrhotite. Petrographic and compositional data for these minerals are interpreted to indicate that all are high-temperature (<900–650°C), early-crystallizing phases from relatively-unevolved natrocarbonatite magma, with the sulphides forming prior to the silicates, and the latter before gregoryite. Sulphur fugacity and oxygen fugacity of natrocarbonatite magma are considered to decrease and increase, respectively, during the formation of the sulphide-oxide assemblage. Crystallization of Cuspidine-niocalite, monticellite and Si-bearing apatite rapidly depletes natrocarbonatite magma of its initial low silica content, preventing crystallization of late-stage groundmass silicates.
Aritza Wainmartin - One of the best experts on this subject based on the ideXlab platform.
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synthesis of new ln4 al2o6f2 o2 ln sm eu gd phases with a Cuspidine related structure
IUCrJ, 2019Co-Authors: Aroa Moranruiz, P R Slater, Aritza Wainmartin, Alodia Orera, M L Sanjuan, Aitor Larranaga, M I ArriortuaAbstract:The first fluorination of the Cuspidine-related phases of Ln4(Al2O7□)O2 (where Ln = Sm, Eu, Gd) is reported. A low-temperature reaction with poly(vinylidene difluoride) lead to the fluorine being substituted in place of oxygen and inserted into the vacant position between the dialuminate groups. X-ray photoelectron spectroscopy shows the presence of the F 1s photoelectron together with an increase in Al 2p and rare-earth 4d binding energies supporting F incorporation. Energy-dispersive X-ray spectroscopy analyses are consistent with the formula Ln4(Al2O6F2)O2, confirming that substitution of one oxygen by two fluoride atoms has been achieved. Rietveld refinements show an expansion in the cell upon fluorination and confirm that the incorporation of fluoride in the Ln4(Al2O7□)O2 structure results in changes in Al coordination from four to five. Thus, the isolated tetrahedral dialuminate Al2O7 groups are converted to chains of distorted square-based pyramids. These structural results are also discussed based on Raman spectra.
