Cation ordering in magnesioferrite, MgFe2O4, to 982 °C using in situ synchrotron X-ray powder diffraction
-
Sytle M. Antao
,
Ishmael Hassan
Abstract
Magnesioferrite spinel, MgFe2O4, was synthesized at 900 °C from equimolar amounts of reagentgrade oxides, MgO and Fe2O3, and quenched in air. The structural behavior of magnesioferrite was determined from in situ synchrotron X-ray powder-diffraction data [λ = 0.92225(4) Å] at room pressure and temperatures from 28 to 982 °C on heating and cooling. The a unit-cell parameter increases linearly on heating, but deviates to give a discontinuity at 581 °C. Above 581 °C and on cooling from 982 °C, the a parameter varies linearly. The a parameter at 28 °C before heating [8.39704(5) Å] and after cooling to 47 °C [8.39514(4) Å] is different because the cation order frozen in the structure is not the same. Cation order, analyzed in terms of the inversion parameter, x, {iv[Mg1-xFex]vi[Mgx/2Fe1-x/2]2O4}, and the order parameter, Q = 1 - (3/2) x, show no change on heating until the temperature is high enough to cause exchange of Mg2+ and Fe3+ cations between the octahedral and tetrahedral sites. This activation barrier is overcome at 581 °C, where the sample achieves the maximum ordered state on heating [Xmax = 0.867(4)] and begins to move toward equilibrium. This relaxation is toward a more ordered configuration and is a kinetically controlled process. Above 581 °C, the cations continuously disorder along the equilibrium pathway to the maximum temperature studied [Tmax = 982 °C, x = 0.769(3)] and reverse along the equilibrium pathway on cooling. At TB, the maximum equilibrium order is frozen in, and maintained to room temperature, where Xmax = 0.895(4). O'Neill-Navrotsky, Landau, and Ginzburg-Landau models give good descriptions of the ordering process in MgFe2O4. Simultaneous differential scanning calorimetry (DSC) and thermogravimetry (TG) data were obtained using a Netzsch STA 449C simultaneous TG-DSC instrument. The DSC curve for MgFe2O4 contains an irreversible exothermic peak at about 550 °C = Trelax in the first heating experiment, and the energy change associated with this peak is -162 J/g (= -32 KJ/mol), and corresponds to cation relaxation. From Rietveld refinements, Trelax ≈ 581 °C. The TCurie ≈ 360 °C was obtained from TG experiments carried out in a magnetic field.
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
- Contact metamorphism of the White Mountain Peak metavolcanic complex, eastern California
- Structure and luminescence characteristics of quartz from pegmatites
- Evidence for monazite-, barite-, and AgMnO4 (distorted barite)-type structures of CaSO4 at high pressure and temperature
- The “template” effect of the extra-framework content on zeolite compression: The case of yugawaralite
- The influence of OH in coesite on the kinetics of the coesite-quartz phase transition
- First-principles study of hydrogen bond symmetrization of phase D under high pressure
- First-principles study of OH-stretching modes in kaolinite, dickite, and nacrite
- A systematic study of OH in hydrous wadsleyite from polarized FTIR spectroscopy and single-crystal X-ray diffraction: Oxygen sites for hydrogen storage in Earthʼs interior
- Determination of the content and distribution of fixed ammonium in illite-smectite using a modified X-ray diffraction technique: Application to oil source rocks of western Greenland
- Determination of defect structures in kaolin minerals by high-resolution transmission electron microscopy (HRTEM)
- Mössbauer spectroscopy of omphacite and garnet pairs from eclogites: Application to geothermobarometry
- Allanite and epidote weathering at the Coweeta Hydrologic Laboratory, western North Carolina, U.S.A.
- Ca2SiO3OHFA high-pressure phase with dense calcium polyhedral packing and tetrahedral silicon
- Relationships between SEM-cathodoluminescence response and trace-element composition of hydrothermal vein quartz
- Quantitative evaluation of attenuation contrast of X-ray computed tomography images using monochromatized beams
- Biotic and abiotic products of Mn(II) oxidation by spores of the marine Bacillus sp. strain SG-1
- The Mn, Mg-intracrystalline exchange reaction in donpeacorite (Mn0.54Ca0.03Mg1.43Si2O6) and its relation to the fractionation behavior of Mn in Fe, Mg-orthopyroxene
- Crystal structures of chalcostibite (CuSbS2) and emplectite (CuBiS2): Structural relationship of stereochemical activity between chalcostibite and emplectite
- Hydration and swelling of synthetic Na-saponites: Influence of layer charge
- Dehydroxylation and CO2 incorporation in annealed mica (sericite): An infrared spectroscopic study
- Relict coesite exsolution in omphacite from Western Tianshan eclogites, China
- Hyperfine electric field gradients and local distortion environments of octahedrally coordinated Fe2+
- A synchrotron Mössbauer spectroscopy study of (Mg,Fe)SiO3 perovskite up to 120 GPa
- Temporal stability and pressure calibration of barium carbonate and talc/pyrex pressure media in a piston-cylinder apparatus
- Cation ordering in magnesioferrite, MgFe2O4, to 982 °C using in situ synchrotron X-ray powder diffraction
- Halite-sylvite thermoconsolution
- The role of water in the structures of synthetic hallimondite, Pb2[(UO2)(AsO4)2](H2O)n and synthetic parsonsite, Pb2[(UO2)(PO4)2](H2O)n, 0 ≤ n ≤ 0.5
- Variable-temperature structural studies of tetranatrolite from Mt. Saint-Hilaire: Synchrotron X-ray powder diffraction and Rietveld analysis
- Letter. Pressure-induced stabilization of ordered paranatrolite: A new insight into the paranatrolite controversy
- Letter. The effect of zinc sulfide on phase transformations of ferrihydrite
- Letter. Stability and equation of state of MgGeO3 post-perovskite phase
- Letter. Pressure dependence of the OH-stretching mode in F-rich natural topaz and topaz-OH
Articles in the same Issue
- Contact metamorphism of the White Mountain Peak metavolcanic complex, eastern California
- Structure and luminescence characteristics of quartz from pegmatites
- Evidence for monazite-, barite-, and AgMnO4 (distorted barite)-type structures of CaSO4 at high pressure and temperature
- The “template” effect of the extra-framework content on zeolite compression: The case of yugawaralite
- The influence of OH in coesite on the kinetics of the coesite-quartz phase transition
- First-principles study of hydrogen bond symmetrization of phase D under high pressure
- First-principles study of OH-stretching modes in kaolinite, dickite, and nacrite
- A systematic study of OH in hydrous wadsleyite from polarized FTIR spectroscopy and single-crystal X-ray diffraction: Oxygen sites for hydrogen storage in Earthʼs interior
- Determination of the content and distribution of fixed ammonium in illite-smectite using a modified X-ray diffraction technique: Application to oil source rocks of western Greenland
- Determination of defect structures in kaolin minerals by high-resolution transmission electron microscopy (HRTEM)
- Mössbauer spectroscopy of omphacite and garnet pairs from eclogites: Application to geothermobarometry
- Allanite and epidote weathering at the Coweeta Hydrologic Laboratory, western North Carolina, U.S.A.
- Ca2SiO3OHFA high-pressure phase with dense calcium polyhedral packing and tetrahedral silicon
- Relationships between SEM-cathodoluminescence response and trace-element composition of hydrothermal vein quartz
- Quantitative evaluation of attenuation contrast of X-ray computed tomography images using monochromatized beams
- Biotic and abiotic products of Mn(II) oxidation by spores of the marine Bacillus sp. strain SG-1
- The Mn, Mg-intracrystalline exchange reaction in donpeacorite (Mn0.54Ca0.03Mg1.43Si2O6) and its relation to the fractionation behavior of Mn in Fe, Mg-orthopyroxene
- Crystal structures of chalcostibite (CuSbS2) and emplectite (CuBiS2): Structural relationship of stereochemical activity between chalcostibite and emplectite
- Hydration and swelling of synthetic Na-saponites: Influence of layer charge
- Dehydroxylation and CO2 incorporation in annealed mica (sericite): An infrared spectroscopic study
- Relict coesite exsolution in omphacite from Western Tianshan eclogites, China
- Hyperfine electric field gradients and local distortion environments of octahedrally coordinated Fe2+
- A synchrotron Mössbauer spectroscopy study of (Mg,Fe)SiO3 perovskite up to 120 GPa
- Temporal stability and pressure calibration of barium carbonate and talc/pyrex pressure media in a piston-cylinder apparatus
- Cation ordering in magnesioferrite, MgFe2O4, to 982 °C using in situ synchrotron X-ray powder diffraction
- Halite-sylvite thermoconsolution
- The role of water in the structures of synthetic hallimondite, Pb2[(UO2)(AsO4)2](H2O)n and synthetic parsonsite, Pb2[(UO2)(PO4)2](H2O)n, 0 ≤ n ≤ 0.5
- Variable-temperature structural studies of tetranatrolite from Mt. Saint-Hilaire: Synchrotron X-ray powder diffraction and Rietveld analysis
- Letter. Pressure-induced stabilization of ordered paranatrolite: A new insight into the paranatrolite controversy
- Letter. The effect of zinc sulfide on phase transformations of ferrihydrite
- Letter. Stability and equation of state of MgGeO3 post-perovskite phase
- Letter. Pressure dependence of the OH-stretching mode in F-rich natural topaz and topaz-OH
