A Technique for Observing Oxygen Diffusion Along Grain Boundary Regions in Synthetic Forsterite
- Robert N. Schock
Published Online: 18 MAR 2013
Copyright 1985 by the American Geophysical Union.
Point Defects in Minerals
How to Cite
Condit, R. H., Weed, H. C. and Piwinskii, A. J. (1985) A Technique for Observing Oxygen Diffusion Along Grain Boundary Regions in Synthetic Forsterite, in Point Defects in Minerals (ed R. N. Schock), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM031p0097
- Published Online: 18 MAR 2013
- Published Print: 1 JAN 1985
Print ISBN: 9780875900568
Online ISBN: 9781118664070
- Mineralogical chemistry—Congresses;
We describe a technique for observing oxygen diffusion into synthetic forsterite, Mg2SiO4. An oxygen-18 isotope tracer was used in a gas-solid interchange anneal. Tracer penetration into Mg2SiO4 was examined by the technique of proton bombardment activation to convert the oxygen-18 into radioactive fluorine-18, followed by autoradiography. This is the first application of this technique to silicate diffusion studies and is concerned with grain boundary regions which contain other phases than the matrix material. High diffusion rates measured at 1374°C are related to the presence of molten material, while at 1107°C there is evidence for penetration of oxygen gas along cracks in the grain boundary region. Our best diffusion coefficient obtained at 1325°C is in general accord with earlier predictions for grain boundary diffusion, albeit higher. This suggests that the grain boundary material is enriched in dislocations and interphase contacts. This technique for observing oxygen-18 tracer should be applicable to studies of grain boundary and dislocation diffusion and to studies of solid-solid and solid-gas reactions.