Kinetics of cation ordering in synthetic MgAl2O4 spinel
-
Giovanni B. Andreozzi
and
Francesco Princivalle
Abstract
The time and temperature evolution of intracrystalline Mg-Al exchange in synthetic MgAl2O4 spinel was studied by single-crystal X-ray diffraction of quenched samples, with the aim of contributing to rock cooling-rate estimation. Flux-grown, homogeneous crystals (0.1 mm in size) were annealed at 1000°C and then were isothermally ordered at 900, 800, and 700°C for 10 seconds to 40 days. The cation ordering process was investigated by measuring the spinel O atom positional parameter u, which had been previously demonstrated to be closely related to the inversion x at equilibrium by the linear equation (R2 = 0.995):
x = 21.396 - 80.714 u.
From x = 0.27 after annealing runs, the inversion decreased with time for all of the three ordering runs, and equilibrium was reached after about 4 min at T = 900°C (x = 0.25), about 55 min at T = 800°C (x = 0.23), and about 700 min at T = 700°C (x = 0.21). The Mueller kinetic model was satisfactorily applied to the experimental data. Solution of Mueller’s integral gave the kinetic ordering constants K900 = 1.12 ± 0.57, K800 = 0.112 ± 0.047, and K700 = 0.0171 ± 0.0045 min-1, corresponding to t1/2 of 0.6, 6.2, and 40.5 min, respectively. The linear dependence of K with temperature (R2 = 0.99) was observed, and may be expressed by the Arrhenius equation:
ln K = 20.189 - 23722/T (K)
An activation energy of 197 ± 22 kJ/mol was obtained for the intracrystalline Mg-Al ordering reaction, which compares well with the value of 217 kJ/mol reported in the recent literature for Mg- Fe3+ exchange in spinels
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Thermal equations of state for B1 and B2 KCl
- Determination of molar absorptivities for infrared absorption bands of H2O in andesitic glasses
- H2O activity in H2O-N2 fluids at high pressure and temperature measured by the brucitepericlase equilibrium
- Kinetics of iron oxidation-reduction in hydrous silicic melts
- Kinetics of cation ordering in synthetic MgAl2O4 spinel
- Structural properties and heat-induced oxidation-dehydrogenation of manganoan ilvaite from Perda Niedda mine, Sardinia, Italy
- Ultrahigh-pressure metamorphism in western Tianshan, China: Part I. Evidence from inclusions of coesite pseudomorphs in garnet and from quartz exsolution lamellae in omphacite in eclogites
- Ultra-high pressure metamorphism in western Tianshan, China: Part II. Evidence from magnesite in eclogite
- Discovery of clinoenstatite in garnet pyroxenites from the Dabie-Sulu ultrahigh-pressure terrane, east-central China
- Ultrahigh-pressure (UHP) low-Al titanites from carbonate-bearing rocks in Dabieshan- Sulu UHP terrane, eastern China
- Metamictization and recrystallization of titanite: An infrared spectroscopic study
- Fine structure of infrared OH-stretching bands in natural and heat-treated amphiboles of the tremolite-ferro-actinolite series
- Correlation between OH concentration and oxygen isotope diffusion rate in diopsides from the Adirondack Mountains, New York
- The substitution Fe3+-Al and the isosymmetric displacive phase transition in synthetic zoisite: A powder X-ray and infrared spectroscopy study
- In situ X-ray observation of the reaction dolomite = aragonite + magnesite at 900–1300 K
- High-pressure single-crystal X-ray and powder neutron study of F,OH/OD-chondrodite: Compressibility, structure, and hydrogen bonding
- Quantitative characterization of biotic iron oxides by analytical electron microscopy
- Synthesis and NMR characterization (1H and 31P MAS) of the fluorine-free hydroxylapatite–britholite-(Y) series
- Quantum mechanical calculations of dioctahedral 2:1 phyllosilicates: Effect of octahedral cation distributions in pyrophyllite, illite, and smectite
- The nature of disorder in montmorillonite by simulation of X-ray powder patterns
- Ferripedrizite, a new monoclinic BLi amphibole end-member from the Eastern Pedriza Massif, Sierra de Guadarrama, Spain, and a restatement of the nomenclature of Mg-Fe-Mn-Li amphiboles
- Description and crystal structure of vajdakite, [(Mo6+O2)2(H2O)2 As3+ 2O5]·H2O—A new mineral from Jáchymov, Czech Republic
- Some remarks on fission-track observational biases and crystallographic orientation effects
- Surface reconstruction and As-polymerization at fractured loellingite (FeAs2) surfaces
- The strength of moissanite
- Diamond formation through carbonate-silicate interaction
- Anisotropic Fe-Mg diffusion in biotite
- Characterization of a high-pressure phase of silica from the Martian meteorite Shergotty
