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  • 1
    Electronic Resource
    Electronic Resource
    Crystal structure and valency properties of superconducting phases of Ba(Pb, Bi, Sb)O"3 perovskites
    Amsterdam : Elsevier
    Physica C: Superconductivity and its applications 202 (1992), S. 379-384 
    Details
    ISSN: 0921-4534
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0921-4534(92)90183-D
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  • 2
    Electronic Resource
    Electronic Resource
    Experimental determination of the upper stability of scorzalite, FeAl2[OH/PO4]2, and the occurrence of minerals with a composition intermediate between scorzalite and lazulite(ss) up to the conditions of the amphibolite facies (1997)
    Springer
    Mineralogy and petrology 61 (1997), S. 211-222 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Das Stabilitätsfeld von Skorzalith (FeAl2[OH/PO4]2) wurde im P-T-Bereich zwischen 487 und 684 °C und zwischen 0.1 und 0.3 GPa in Hydrothermalexperimenten unter der Sauerstoffugazität des Ni/NiO-Puffers untersucht. Skorzalith zerfällt unter diesen Bedingungen gemäß der Reaktion: FeAl2[OH/PO4]2) → FeAlPO5 + AlPO4 (Berlinit) + H2O. Die Reaktionsenthalpie und -entropie für Standardbedingungen wurden zu ΔH R 0 = 94(13) kJ und ASR = 180(16) JK−1 bestimmt.57 Fe-Mößbaueruntersuchungen ergaben, daß ungefähr 4% des Gesamteisens in Skorzalith dreiwertig vorliegen.
    Notes: Summary The stability field of scorzalite (FeAl2[OH/PO4]2) was investigated in the P-T range from 487 to 684 °C and 0.1 to 0.3 GPa. in hydrothermal experiments. The oxygen fugacity was fixed by the Ni/NiO buffer. Scorzalite shows a decomposition according to the reaction: FeAl2[OH/PO4]2) → FeAlPO5 + AlPO4 (berlinite) + H2O. The mean standard enthalpy and standard entropy of reaction were determined as ΔH R 0 = 94(13) kJ, ASR = 180(16) JK−1. A57Fe-Mößbauer spectroscopic examination showed that about 4 atomic % of the total Fe in scorzalite is trivalent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01172485
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  • 3
    Electronic Resource
    Electronic Resource
    P-T stability of the lazulite-scorzalite solid-solution series (2000)
    Springer
    Mineralogy and petrology 70 (2000), S. 55-71 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung P-T Stabilität von Lazulith-Scorzalith Mischkristallen Die Stabilität der Glieder der Lazulith-Scorzalith Mischkristallreihe, (Mg, Fe)Al2(OH)2(PO4)2 wurde als Funktion der Temperatur (505 bis 675 °C), des Druckes (0.1 bis 0.3 GPa) und des Fe/Mg-Verhältnisses in hydrothermalen Syntheseversuchen untersucht. Die Sauerstoffugazität wurde mittels eines Ni/NiO-Puffer kontrolliert. Es konnte festgestellt werden, daß ausgehend vom Lazulith-Endglied die Stabilität der Mischkristalle mit zunehmendem Scorzalith-Gehalt stark abnimmt. Reiner Lazulith, MgAl2(OH)2(PO4)2 zerfällt unter 0.2 GPa bei 660 °C, während ein Mischkristall mit 80 mol% Gehalt an Lazulith-Komponente nur bis 590 °C unter der Sauerstoffugazität des Ni/NiO-Puffers stabil ist. Hierbei koexistieren die Lazulith-Scorzalith Mischkristalle mit Grenzzusammensetzung mit eisenreicheren Mischphasen des Systems (Mg,Fe)Al(PO4)2O und Berlinit. Das Mischungsverhalten sowohl der Lazulith-Scorzalith- als auch der (Mg,Fe)Al(PO4)2O-Reihe wurde mit Hilfe eines quantitativen Modelles auf der Basis einer symmetrischen Mischung für Lazulith-Scorzalith und einer idealen Mischung für das System (Mg,Fe)Al(PO4)2O interpretiert. Mit Hilfe dieses Modelles wurde der Wechelwirkungsparameter , der die Nichtidealität der Lazulith-Scorzalith Mischreihe ausdrückt zu bestimmt.
    Notes: Summary The stability of members of the lazulite-scorzalite solid-solution series, (Mg,Fe)Al2 (OH)2(PO4)2, was investigated as a function of T (505 to 675 °C), P (0.1 to 0.3 GPa) and Fe/Mg ratio in hydrothermal synthesis experiments. The oxygen fugacity was controlled by means of the Ni/NiO buffer. It was found that starting from end-member lazulite the stability of the solid-solution members strongly decreases with increasing content of scorzalite component. At 0.2 GPa pure lazulite decomposes at about 660 °C whereas at the same pressure a solid-solution with 80% of lazulite component is only stable up to 590 °C under the oxygen fugacity of the Ni/NiO buffer. The members of the lazulite-scorzalite solid-solution series with limiting composition coexist with an Fe-richer member of the (Mg,Fe)Al(PO4)O series and berlinite. The mixing behaviour of both the lazulite-scorzalite and the (Mg,Fe)Al(PO4)O solid-solution series disregarding small amounts of Fe3+ is interpreted in terms of a model on the basis of a simple mixture for the lazulite-scorzalite system and of an ideal mixture for the (Mg,Fe)Al(PO4)O series. With this model the interaction parameter which expresses the non-ideality of the lazulite-scorzalite solid-solution series amounts to .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007100070013
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  • 4
    Electronic Resource
    Electronic Resource
    Stability properties of the CuS2-FeS2 solid solution series of pyrite type (1995)
    Springer
    Mineralogy and petrology 53 (1995), S. 333-341 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Stabilität der CuS2-FeS2 Mischreihe des Pyrit-Typs Experimentelle Untersuchungen zur Cu-Fe-Substitution und zur Bildung einer festen Lösung im System CuS2-FeS2 wurden mit der Hydrothermalsynthese bis 350°C und 3 kb und mit der Stempelzylindermethode bis 900°C und 45 kb durchgeführt. Unter trockenen Bedingungen bei 440°C und oberhalb 17 kb ist dieses System binär und weist eine Mischungslücke zwischen einer eisenreichen Phase nahe dem FeS2 Endglied und einer koexistierenden kupferreichen Phase mit der Solvuszusammensetzung eines Homogenitätsbereiches zwischen 75 und 100 mol% CuS2 auf. Dieser Solvus der kupferreichen Phase wurde bis 45 kb und 700°C nahezu druck- und temperaturunabhängig gefunden. Demgegenüber nimmt die Löslichkeit von CuS2 in FeS2 bei 45 kb von 0.6 mol% bei 700°C auf 4.5 mol% bei 900°C zu. Der Solvus der metastabilen (Cu, Fe)S2-Phasen, die bislang nur unter hydrothermalen Bedingungen synthetisiert werden können, zeigte bis 3 kbar nur im kupferreichen Teil des Systems eine starke Druckabhängigkeit.
    Notes: Summary Experimental investigations on the Cu-Fe-substitution and the formation of a solid solution series in the system CuS2-FeS2 were carried out under hydrothermal conditions up to 350°C and 3 kb and by means of a piston cylinder apparatus at higher temperatures and pressures up to 900°C and 45 kb. Under dry conditions at 440°C and above 17 kb the system was found to be binary with a miscibility gap between an iron-rich phase near the FeS2 end-member and a coexisting copper-rich phase being the solvus composition of a homogeneity region from 75 to 100 mole% CuS2. This solvus of the copper rich phase was found to be almost independent of temperature and pressure up to 45 kb and 700°C. The solubility of CuS2 in FeS2 at 45 kb increases from 0.6 mole% at 700°C to 4.5 mole% at 900°C. Under hydrothermal conditions up to 3 kbars the solvus of metastable (Cu, Fe)S2 is strongly dependent on pressure only in the Cu-rich part of the system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01160155
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  • 5
    Electronic Resource
    Electronic Resource
    Crystal chemical properties of synthetic lazulite–scorzalite solid-solution series (1999)
    Springer
    Physics and chemistry of minerals 26 (1999), S. 496-505 
    Details
    ISSN: 1432-2021
    Keywords: Key words Phosphate minerals ; Lazulite ; Scorzalite ; Solid-solution ; 57Fe-Mössbauer spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Members of the lazulite–scorzalite (MgAl2- (PO4)2(OH)2-FeAl2(PO4)2(OH)2) solid-solution series were synthesized in compositional steps of 12.5 mol% at T = 485 °C and P = 0.3 GPa under hydrothermal conditions and controlled oxygen fugacities of the Ni/NiO-buffer. X-ray powder diffraction and 57Fe-Mössbauer studies show that under these conditions a complete solid-solution series is formed which is characterized by the substitution of Mg2+ and Fe2+ on the octahedral Me 2+ site. The 57Fe-Mössbauer spectra which reveal the presence of both ferrous and ferric iron and the compositional data were interpreted in terms of a defect model with a distribution of the ferric ions over both the Me 2+ and the Al3+ positions and vacancies on the Me 2+ site. The 57Fe-Mössbauer parameters of the synthetic compounds correspond to those of natural lazulites except for the total absorption ratio of the ferric iron A(Fe3+)/(A(Fe3+)+A(Fe2+)), which is significantly higher in natural lazulites of the same composition. The total absorption ratio of the ferric iron increases from 4% in pure scorzalite to 15% in a Mg-rich solid-solution with x Fe  = 12(1)%
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050212
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  • 6
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    Crystal structure and valency properties of superconducting phases of Ba(Pb, Bi, Sb)O3 perovskites (1992)
    Elsevier
    Details
    Publication Date: 1992-11-01
    Print ISSN: 0921-4534
    Electronic ISSN: 1873-2143
    Topics: Physics
    Published by Elsevier
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  • 7
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    Thermal expansion and thermal pressure in Co and Ni olivines: A comparison with Mn and Fe olivines (2019)
    Schweizerbart
    Details
    Publication Date: 2019
    Description: 〈span〉To complete the data basis for comparing the thermal behaviour of end-member olivines containing cations of the transition element series Mn (3d〈sup〉5〈/sup〉), Fe (3d〈sup〉6〈/sup〉), Co (3d〈sup〉7〈/sup〉), Ni (3d〈sup〉8〈/sup〉 subshell) the thermal expansivity of Co and Ni olivines has been studied by X-ray powder diffraction at ambient pressure and temperatures between 25 °C and 1000 °C. The anisotropy of the thermal expansion was analysed using the Kumar isothermal equation-of-state (EoS) coupled with the thermal Mie-Grüneisen EoS. For Co olivine, in order to stabilize the refinement of the EoS coefficients, our thermal expansion data were combined in a simultaneous fit with published 〈span〉P〈/span〉(〈span〉a, b, c, V〈/span〉) and axial and bulk 〈span〉K〈/span〉〈sup〉〈span〉T〈/span〉〈/sup〉 (〈span〉T〈/span〉) data. This reduced correlations between parameters considerably. Analogous pressure and moduli data for Ni olivine are lacking so that only unit-cell data could be fitted. The volume-related EoS coefficients of Co olivine are  K0T=143.7(3) GPa, K0T′=5.0(2), γ0MG=1.23(1), V0=295.69(5) Å〈sup〉3〈/sup〉 with the acoustic Debye temperature fixed at 551 K. Axial expansivities α are controlled by compressibilities β〈sub〉〈span〉T〈/span〉〈/sub〉 and thermal pressures (∂〈span〉P〈/span〉/∂〈span〉T〈/span〉)〈sub〉〈span〉V〈/span〉〈/sub〉 according to α 〈span〉=〈/span〉 β〈sub〉〈span〉T〈/span〉〈/sub〉 (∂〈span〉P〈/span〉/∂〈span〉T〈/span〉)〈sub〉〈span〉V〈/span〉〈/sub〉. For olivines, the structural features suggest a sequence of compressibilities with β〈sub〉〈span〉T,b〈/span〉〈/sub〉 〉 β〈sub〉〈span〉T,c〈/span〉〈/sub〉 〉 β〈sub〉〈span〉T,a〈/span〉〈/sub〉 (SG 〈span〉Pbnm〈/span〉). Usually, a similar ranking is also found for the axial expansivities. In the case of olivines, however, only Mn olivine meets the expectation, contrary to Fe olivine and to a lesser extent to Co and Ni olivine. The reason for the unusual behaviour is found in the specific anisotropies of the axial thermal pressures. Extrapolation of thermal expansivities and of linear and bulk moduli is justified up to 2200 K, judged from the fulfillment of the relations 1/K VT=1/3K aT+1/3K bT+1/3K cT and αV(T)=αa(T)+αb(T)+αc(T).〈/span〉
    Print ISSN: 0935-1221
    Electronic ISSN: 1617-4011
    Topics: Geosciences
    Published by Schweizerbart
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  • 8
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    CoMg olivine: cation partitioning, thermal expansion and structural variation studied by in situ neutron and synchrotron powder diffraction (2016)
    Schweizerbart
    Details
    Publication Date: 2016-11-15
    Description: The crystal structure of CoMg olivine has been investigated by in situ neutron and synchrotron X-ray powder diffraction at temperatures between 23°C and 1050°C. The olivine sample was prepared at 1450°C by solid-state reaction. During quench, the structure acquired a partially anti-ordered Co,Mg site occupancy, $${X}_{\mathrm{Co}}^{\mathrm{M}1} 〉 {X}_{\mathrm{Co}}^{\mathrm{M}2}$$ , which upon ensuing heating persisted up to 550°C due to slow exchange kinetics. Above 600°C, internal equilibrium was readily obtained. The temperature variation of the Co,Mg site occupancies was modelled by R T ln( K D ) = –12080(±620) = 1.60(±0.58) T [J mol –1 ]. The pronounced negative exchange enthalpy strongly favours the anti-ordered state, as does the positive exchange entropy so that CoMg olivine will remain in this state up to the melting point. The anisotropy of thermal expansion was analysed using an isothermal equation-of-state (EoS) ( Kumar, 1995 ) coupled with the thermal Mie-Grüneisen EoS. This coupling allowed for relating the anisotropic expansivity to an anisotropic thermal pressure. Both properties are linked to the temperature-dependent rotations of the M1 and M2 octahedra in the [001] plane. The rotations increase from Mg via CoMg to Fe olivine. The Kumar and Birch-Murnaghan EoS’s gave virtually indistinguishable results upon modelling thermal expansion. The increase of the mean bond distances 〈M1-O〉 and 〈M2-O〉 with temperature changes at ~550°C when the redistribution of Co and Mg begins. In terms of a distortion parameter defined as a normalized standard deviation, the bond length distortion of the M2 octahedron is larger than that of M1. Conversely, M1 is more distorted than M2, if the distortion is defined by the variation of the octahedral faces as well as by the variation of the O-M-O angles subtended at the M sites. The former distortion relates to the exchange entropy.
    Print ISSN: 0935-1221
    Electronic ISSN: 1617-4011
    Topics: Geosciences
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  • 9
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    Triphylite-Sarcopside Miscibility Gap In the FeO-MnO-Li2O-P2O5-H2O System: Experimental Investigation and Thermometric Application To Granitic Pegmatites (2017)
    Mineralogical Association of Canada
    Details
    Publication Date: 2017-05-27
    Description: In order to assess the stability of the primary triphylite + sarcopside assemblage, we performed hydrothermal experiments between 400 and 700 °C (Ni/NiO oxygen fugacity buffer, P = 1 kbar), starting from the Li(Fe 2+ 2.5– x Mn 2+ x )(PO 4 ) 2 ( x = 0.0, 0.5, 1.0) compositions, which represent the ideal compositions of triphylite + sarcopside assemblages in which both minerals occur in a 1:1 molar ratio. The triphylite + sarcopside assemblage is observed in all experiments, associated with other phosphates like (Fe 2+ ,Mn 2+ ) 2 P 2 O 7 , (Fe 2+ ,Mn 2+ )Fe 3+ 2 (PO 4 ) 2 (OH) 2 · n H 2 O, or Fe 3+ 4 (Fe 2+ ,Mn 2+ ) 3 (PO 4 ) 6 . Electron-microprobe and SIMS analyses show a progressive decrease of the Li contents in the triphylites, balanced by an increase of their Fe 2+ -contents, when the temperature increases. These compositional changes are due to the increase of the triphylite–sarcopside miscibility along the Li 2 (Fe 2+ ,Mn 2+ ) 2 (PO 4 ) 2 –Fe 2+ (Fe 2+ ,Mn 2+ ) 2 (PO 4 ) 2 solid solution; the experimental phase diagrams can consequently be used as a geothermometer to calculate the exsolution temperatures of the assemblages. A linear fit of the experimental data leads to the general equation: T (°C) = (–142 * XFe) – (773 * Li pfu ) + 1131, where XFe = Fe/(Fe + Mn). The uncertainty is around ±15 °C, and the influence of pressure is assumed to be negligible. By using this equation, exsolution temperatures were calculated for nine triphylite–sarcopside assemblages from pegmatites; these temperatures do not represent the crystallization temperatures of the phosphate nodules, but correspond to the closing temperature of the triphylite–sarcopside element exchange. Nevertheless, these temperatures, between 276 and 397 °C, are in fairly good agreement with those generally accepted for the crystallization of primary phosphate assemblages in granitic pegmatites.
    Print ISSN: 0008-4476
    Topics: Geosciences
    Published by Mineralogical Association of Canada
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  • 10
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    Synthesis and Phase Characterization of a Solid Solution Series between β-Fe2(PO4)O and Fe4(PO4)3(OH)3 (2000)
    Elsevier
    Details
    Publication Date: 2000-09-01
    Print ISSN: 0022-4596
    Electronic ISSN: 1095-726X
    Topics: Chemistry and Pharmacology
    Published by Elsevier
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