X-ray single-crystal study of spinels: in situ heating

Carbonin, S.; Martignago, F.; Menegazzo, G.; Negro, A. Dal

doi:10.1007/s00269-002-0262-6

Cited by 64 publications

(68 citation statements)

References 7 publications

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“…In the next step, the structural parameters such as lattice parameters, profile shape and width parameters, preferred orientation, asymmetry, isothermal parameters, atomic coordinates, and site occupancies were refined in sequence. The fitting quality of the experimental data is assessed by computing the parameters such as the 'goodness of fit' χ 2 and the R factors (R p = profile factor, R B = Bragg factor, and R F = crystallographic factor) [20]. When these parameters reached their minimum value, the best fit to the experimental diffraction data is achieved, and the crystal structure is regarded as satisfactory [20].…”

Section: Powder X-ray Diffraction Studymentioning

confidence: 99%

“…The fitting quality of the experimental data is assessed by computing the parameters such as the 'goodness of fit' χ 2 and the R factors (R p = profile factor, R B = Bragg factor, and R F = crystallographic factor) [20]. When these parameters reached their minimum value, the best fit to the experimental diffraction data is achieved, and the crystal structure is regarded as satisfactory [20]. The site occupancies of the cations in the two interstitial sites (tetrahedral and octahedral sites) are constrained so as to preserve the stoichiometric composition of the materials.…”

Section: Powder X-ray Diffraction Studymentioning

confidence: 99%

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Rietveld analysis of XRD patterns of different sizes of nanocrystalline cobalt ferrite

et al. 2013

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Nanocrystalline cobalt ferrite powder has been synthesised by citrate precursor and co-precipitation methods. Structural characterization of the samples has been carried out using powder X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR) and field emission scanning electron microscope (FE-SEM). Distribution of cations among the two interstitial sites (tetrahedral and octahedral sites) has been estimated by analysing the powder X-ray diffraction patterns by employing Rietveld refinement technique, and the results reveal the existence of samples as a mixed type spinel with cubic structure. It is observed that the distribution of cations and structural parameters are strongly dependent on synthesis method and annealing temperature. The vibrational modes of the octahedral and tetrahedral metal complex in the sample have been examined using FT-IR in the wave number range of 390 to 750 cm, and it shows an absorption band within this range, which confirms the spinel structure of the sample. The existence of constituents in the sample, i.e., Co, Fe and O has been authenticated using energy dispersive spectrum with the help of a FE-SEM.

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Section: Powder X-ray Diffraction Studymentioning

confidence: 99%

Section: Powder X-ray Diffraction Studymentioning

confidence: 99%

Rietveld analysis of XRD patterns of different sizes of nanocrystalline cobalt ferrite

et al. 2013

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“…The u parameter was chosen to monitor the evolution of the spinel structural state as it can be measured routinely with both extreme accuracy and precision. Cation distribution at each temperature was obtained using the bond-length model, applying thermal expansion to pure bond lengths (Carbonin et al 2002).…”

Section: Introductionmentioning

confidence: 99%

“…At low temperature, i tends to 0 in normal spinels [e.g., spinel s.s. IV (Mg) VI (Al) 2 O 4 ] and to 1 in inverse spinels [e.g., magnesioferrite IV (Fe 3+ ) VI (MgFe 3+ )O 4 ], which are both ordered. At high temperature, cation disorder increases and i values have been shown to converge asymptotically toward 2/3 for all compositions (Harrison et al 1998;O'Neill et al 1992;O'Neill and Dollase 1994;Redfern et al 1999;Andreozzi et al 2000;Carbonin et al 2002;Martignago et al 2003).The infl uence of non-Al cations on the Mg-Al order-disorder reaction has been recently studied by Martignago et al (2003) using a natural, highly ordered, Fe 3+ -bearing spinel. Their results indicate that the Fe 3+ cation triggers trivalent-divalent cation exchange at T ≥ 550 °C.…”

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confidence: 97%

Thermodynamics and kinetics of cation ordering in natural and synthetic Mg(Al,Fe3+)2O4 spinels from in situ high-temperature X-ray diffraction

Martignago

Andreozzi

Negro

2006

American Mineralogist

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Spinel-group minerals are characterized by a non-convergent, temperature-dependent cation order/disorder, i.e., no change of symmetry is associated with cation disordering. Cation distribution can be described by the IV (A 1-i B i ) VI (B 2-i A i )O 4 structural formula, where IV and VI represent the tetrahedrally and octahedrally coordinated T and M sites, respectively, A and B are cations with different valences, and i represents the inversion parameter. At low temperature, i tends to 0 in normal spinels [e.g., spinel s.s. IV (Mg) VI (Al) 2 O 4 ] and to 1 in inverse spinels [e.g., magnesioferrite IV (Fe 3+ ) VI (MgFe 3+ )O 4 ], which are both ordered. At high temperature, cation disorder increases and i values have been shown to converge asymptotically toward 2/3 for all compositions (Harrison et al. 1998;O'Neill et al. 1992;O'Neill and Dollase 1994;Redfern et al. 1999;Andreozzi et al. 2000;Carbonin et al. 2002;Martignago et al. 2003).The infl uence of non-Al cations on the Mg-Al order-disorder reaction has been recently studied by Martignago et al. (2003) using a natural, highly ordered, Fe 3+ -bearing spinel. Their results indicate that the Fe 3+ cation triggers trivalent-divalent cation exchange at T ≥ 550 °C. This agrees with the results obtained by Andreozzi et al. (2001) for the synthetic spinel-magnesioferrite series, which showed that Fe 3+ partitions between the M and T sites as a function of both magnesioferrite component and temperature. Moreover, Martignago et al. (2003) observed that at the lowest temperatures order-disorder is controlled by a two-stage kinetic process, with a rapid intersite exchange of Fe 3+ with Mg followed by a slow exchange of Mg with Al.Andreozzi and Princivalle (2002) quantitatively described the kinetics of Mg-Al exchange in MgAl 2 O 4 spinel using the Mueller (1967, 1969) model. Following O'Neill (1994, these authors described the order-disorder process with the chemical exchange reaction IV Al + VI Mg = IV Mg + VI Al, the forward reaction accounting for the exchange of Al at the T site with Mg at the M site (ordering), and the backward reaction for the exchange of Mg at the T site with Al at the M site (disordering). These homogeneous reactions were assumed to be second-order chemical reactions, and fi rst-order with respect to the concentration at one site (Ganguly 1982). The time rate of change of concentration of Al at the T site (= i), was expressed as -di/dt = K[i 2 -K D (1-i)(2-i)], where K D , the equilibrium constant of the exchange reaction, is a function of temperature and pressure alone. The variation of i with time was revealed to only depend on the initial and fi nal inversion degrees, and on the rate constant K. The kinetics of Mg-Fe 3+ exchange in MgFe 2 O 4 spinel was * ABSTRACT One natural and two synthetic spinels with compositions Mg(Al 1-z Fe z 3+ ) 2 O 4 (with 2z = 0.078, 0.138, and 0.200, respectively) were studied by in situ, high-temperature, single-crystal X-ray diffraction. All samples were heated from room temperature to 1050 °C. Thermal expansi...

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“…There has been excellent agreement on the T effect on the Mg-Al disorder process of the MgAl2O4-Sp at ambient P: x increases as T increases [42,47,48,50,51,[53][54][55][56][57]. As to the P effect at ambient T, discrepancy presumably exists because the order-disorder reaction could not be readily activated and did not adequately approach its equilibrium during the course of a conventional high-P study [52,90,91].…”

Section: Mg-al Order-disorder State Of Synthetic Mgal2o4-spmentioning

confidence: 99%

Si-Disordering in MgAl2O4-Spinel under High P-T Conditions, with Implications for Si-Mg Disorder in Mg2SiO4-Ringwoodite

Liu

Bao

et al. 2018

Minerals

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A series of Si-bearing MgAl 2 O 4 -spinels were synthesized at 1500-1650 • C and 3-6 GPa. These spinels had SiO 2 contents of up to~1.03 wt % and showed a substitution mechanism of Si 4+ + Mg 2+ = 2Al 3+ . Unpolarized Raman spectra were collected from polished single grains, and displayed a set of well-defined Raman peaks at~610, 823, 856 and 968 cm −1 that had not been observed before. Aided by the Raman features of natural Si-free MgAl 2 O 4 -spinel, synthetic Si-free MgAl 2 O 4 -spinel, natural low quartz, synthetic coesite, synthetic stishovite and synthetic forsterite, we infer that these Raman peaks should belong to the SiO 4 groups. The relations between the Raman intensities and SiO 2 contents of the Si-bearing MgAl 2 O 4 -spinels suggest that under some P-T conditions, some Si must adopt the M-site. Unlike the SiO 4 groups with very intense Raman signals, the SiO 6 groups are largely Raman-inactive. We further found that the Si cations primarily appear on the T-site at P-T conditions ≤~3-4 GPa and 1500 • C, but attain a random distribution between the T-site and M-site at P-T conditions ≥~5-6 GPa and 1630-1650 • C. This Si-disordering process observed for the Si-bearing MgAl 2 O 4 -spinels suggests that similar Si-disordering might happen to the (Mg,Fe) 2 SiO 4 -spinels (ringwoodite), the major phase in the lower part of the mantle transition zone of the Earth and the benchmark mineral for the very strong shock stage experienced by extraterrestrial materials. The likely consequences have been explored.

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X-ray single-crystal study of spinels: in situ heating

Cited by 64 publications

References 7 publications

Rietveld analysis of XRD patterns of different sizes of nanocrystalline cobalt ferrite

Rietveld analysis of XRD patterns of different sizes of nanocrystalline cobalt ferrite

Thermodynamics and kinetics of cation ordering in natural and synthetic Mg(Al,Fe3+)2O4 spinels from in situ high-temperature X-ray diffraction

Si-Disordering in MgAl2O4-Spinel under High P-T Conditions, with Implications for Si-Mg Disorder in Mg2SiO4-Ringwoodite

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