Diffusion in yttrium aluminium garnet at the nanometer-scale: Insight into the effective grain boundary width

Marquardt, Katharina; Ramasse, Quentin M.; Kisielowski, Christian; Wirth, Richard

doi:10.2138/am.2011.3625

Cited by 16 publications

(9 citation statements)

References 64 publications

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“…Joesten 1991). Recent TEM investigations suggest values up to 10 nm for the effective grain boundary width, where 1 nm corresponds rather to the structural grain boundary width (Marquardt et al 2011). It is not possible to assign a definite value here due to possible presence of intergranular fluid films with different widths as a function of water fraction.…”

Section: Analysis Of Reaction Kineticsmentioning

confidence: 92%

The effect of water on intergranular mass transport: new insights from diffusion-controlled reaction rims in the MgO–SiO2 system

Gardès

Wunder

Marquardt

et al. 2012

Contrib Mineral Petrol

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We experimentally investigate the effect of water on intergranular mass transport. The growth of enstatite single rims between forsterite and quartz and forsterite-enstatite double rims between periclase and quartz was performed at 1,000°C and 1.5 GPa for incremental water-solid fractions ranging from 0 to 5 wt%. A kinetics analysis based on time series ranging from 8 min to 18 h at 1 wt% H 2 O demonstrates that the growth of both the single and double rims is controlled by the transport of the chemical components in the intergranular medium. Inert platinum markers reveal that MgO is always the most mobile component, and the only one, except at the highest water fractions ([*2 wt%) where some mobility of SiO 2 is observed. Modelling yields that, in all of the rims from both the single and double rims, there is an increase by about six orders of magnitude between diffusivities in dry grain boundaries and in intergranular media with 5 wt% H 2 O of the bulk, therefore confirming that water/rock ratio is a parameter as important as temperature regarding reaction kinetics. The transition from dry to water-saturated conditions appears virtually instantaneous, occurring between 500 and 1,000 wt. ppm water-solid fraction. It corresponds to a jump of four to five orders of magnitude in diffusivities, in line with the gap between 'dry' and 'wet' enstatite single rim growth rates from various previous experimental investigations. At higher water-solid fractions, distinct increase in the diffusivities demonstrates the existence of two different intergranular transport mechanisms competing at water-saturated conditions. The first mechanism is diffusion in hydrous-saturated grain boundaries (HGBs), which dominates as long as pores are isolated. We estimate the Arrhenius law for MgO diffusion in enstatite HGBs to be d HGB D MgO HGB ¼ d HGB D 0 e ÀE=RT with E = 185 ± 20 kJ/mol and d HGB D 0 = 10 -14.7±0.9 m 3 /s, where d HGB is the effective width of the HGBs. The second mechanism is diffusion through fluid-filled channels, which dominates when pores are interconnected. A new description of the effect of water on intergranular mass transport is proposed.

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Section: Analysis Of Reaction Kineticsmentioning

confidence: 92%

The effect of water on intergranular mass transport: new insights from diffusion-controlled reaction rims in the MgO–SiO2 system

Gardès

Wunder

Marquardt

et al. 2012

Contrib Mineral Petrol

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“…1 nm to regions as wide as several µm (e.g. Mistler and Coble, 1974;Hirth and Kohlstedt, 2003;Marquardt et al, 2011d;Hashim, 2016). Constituting equations for diffusional or rheological processes include the effective grain boundary width, as an imperative parameter (Farver et al, 1994;Kaur et al, 1995;Dillon and Harmer, 2007).…”

Section: Grain Boundary Energy Structure and Widthmentioning

confidence: 99%

“…The effective grain boundary width and the width of the region elements partition to (segregated) are affected by: (1) lattice misfit of the adjacent grains, (2) misfit lattice strain due to the difference between the size of a solute ion and that of the ideal strain-free lattice site Marquardt et al, 2011d;Lejcek, 2010), and (3) in ionic crystals a space charge layer can be present (e.g. Lehovec, 1953;Kliewer and Koehler, 1965;Kingery, 1974).…”

Section: Grain Boundary Energy Structure and Widthmentioning

confidence: 99%

The structure and composition of olivine grain boundaries: 40 years of studies, status and current developments

Marquardt

Faul

2018

Phys Chem Minerals

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Interfaces in rocks, especially grain boundaries in olivine dominated rocks, have been subject to about 40 years of studies. The grain boundary structure to property relation is fundamental to understand the diverging properties of polycrystalline samples compared to those of single crystals. The number of direct structural observations is small, i.e. in range of 100 micrographs, and the number of measurements of properties directly linked to structural observations is even smaller. Bulk aggregate properties, such as seismic attenuation and electrical conductivity are sensitive to grain size, and seem to show influences by grain boundary character distributions. We review previous studies on grain boundary structure and composition and plausible relations to bulk properties. Experimentally determined seismic properties and rheology of olivine are sensitive to grain boundary characteristics. The grain boundary geometry is described using five independent parameters, generally their structural width is ranges between 0.4-1.2 nm and

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“…MgO provides an efficient mechanism to exchange these elements between the mantle and the core even on the kilometer scale within reasonable timescales Watson, 2007, 2008). Furthermore, segregated elements can change the grain boundary structure by influencing atomic bonds and/or vacancy concentrations Mei and Kohlstedt, 2000). Thus, physical grain boundary properties change as a consequence of segregation.…”

Section: Introductionmentioning

confidence: 99%

Grain boundary diffusion and its relation to segregation of multiple elements in yttrium aluminum garnet

2020

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Abstract. We studied grain boundary diffusion and segregation of La, Fe, Mg, and Ti in a crystallographically defined grain boundary in yttrium aluminum garnet (YAG). Bi-crystals were synthesized by wafer bonding. Perpendicular to the grain boundary, a thin-film diffusion source of a La3.60Al4.40O12 was deposited by pulsed laser deposition. Diffusion anneals were performed at 1000 and 1450 ∘C. Via a gas phase small amounts of elements were added during the experiment. The element concentration distributions in our bi-crystals were mapped using analytical transmission electron microscopy (ATEM). Our results show strong segregation of La and Ti at the grain boundary. However, in the presence of Ti, the La concentrations dropped below the detection limit. Quantitative element distribution profiles along and across the grain boundary were fitted by a numerical diffusion model for our bi-crystal geometry that considers the segregation of elements into the grain boundary. The shape of the diffusion profiles of Fe requires the presence of two diffusion modes, e.g., the co-diffusion of Fe2+ as well as Fe3+. The absence of a detectable concentration gradient along the grain boundary in many experiments allows a minimum value to be determined for the product of sDgb. The resulting sDgb are a minimum of 7 orders of magnitude larger than their respective volume diffusion coefficient, specifically for La = 10−14 m2 s−1, Fe = 10−11 m2 s−1, Mg = Si = 10−12 m2 s−1, and Ti = 10−14 m2 s−1 at 1450 ∘C. Additionally, we model the effect of convolution arising from the given spatial resolution of our analysis with the resolution of our modeled system. Such convolution effects result in a non-unique solution for the segregation coefficient, e.g., for example for Mg between 2–3. Based on our data we predict that bulk diffusion of impurities in a mono-phase polycrystalline aggregate of YAG is effectively always dominated by grain boundary diffusion.

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Diffusion in yttrium aluminium garnet at the nanometer-scale: Insight into the effective grain boundary width

Cited by 16 publications

References 64 publications

The effect of water on intergranular mass transport: new insights from diffusion-controlled reaction rims in the MgO–SiO2 system

The effect of water on intergranular mass transport: new insights from diffusion-controlled reaction rims in the MgO–SiO2 system

The structure and composition of olivine grain boundaries: 40 years of studies, status and current developments

Grain boundary diffusion and its relation to segregation of multiple elements in yttrium aluminum garnet

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