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Grain boundary and lattice diffusion of /sup 51/Cr in alumina and spinel

John Osenbach,V. S. STUBIČAN-1982-01-01-OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information)
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TL;DRAbstract

The grain boundary diffusion parameter, ..cap alpha..D'delta, which is the product of the segregation coefficient, the grain boundary diffusion coefficient and the boundary width has been measured in the temperature region 1200 to 1600/sup 0/C along low angle and high angle grain boundaries of Al/sub 2/O/sub 3/ and MgAl/sub 2/O/sub 4/. The activation energies for /sup 51/Cr grain boundary diffusion in Al/sub 2/O/sub 3/ and MgAl/sub 2/O/sub 4/ are 170 +- 10kJ/mole and 185 +- 10kJ/mole respectively, which is approx. 0.55 time the activation energy for the lattice diffusion. The grain boundary diffusivity was strongly dependent on the grain boundary orientation. The ratio of D'/sub parallel/ parallel to D'/sub perpendicular to/ perpendicular to the growth direction, D'/sub parallel to/D'/sub perpendicular to/, is approx. 23 for a 6/sup 0/(0112) Al/sub 2/O/sub 3/ tilt boundary and approx. 2 for a 13/sup 0/(0112) Al/sub 2/O/sub 3/ tilt boundary. The same ratio is approx. 87 for a 4.8/sup 0/

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The grain boundary diffusion parameter, ..cap alpha..D'delta, which is the product of the segregation coefficient, the grain boundary diffusion coefficient and the boundary width has been measured in the temperature region 1200 to 1600/sup 0/C along low angle and high angle grain boundaries of Al/sub 2/O/sub 3/ and MgAl/sub 2/O/sub 4/. The activation energies for /sup 51/Cr grain boundary diffusion in Al/sub 2/O/sub 3/ and MgAl/sub 2/O/sub 4/ are 170 +- 10kJ/mole and 185 +- 10kJ/mole respectively, which is approx. 0.55 time the activation energy for the lattice diffusion. The grain boundary diffusivity was strongly dependent on the grain boundary orientation. The ratio of D'/sub parallel/ parallel to D'/sub perpendicular to/ perpendicular to the growth direction, D'/sub parallel to/D'/sub perpendicular to/, is approx. 23 for a 6/sup 0/(0112) Al/sub 2/O/sub 3/ tilt boundary and approx. 2 for a 13/sup 0/(0112) Al/sub 2/O/sub 3/ tilt boundary. The same ratio is approx. 87 for a 4.8/sup 0/

Keywords

Grain boundary diffusion coefficientGrain boundaryEffective diffusion coefficientCrystallographyLattice diffusion coefficientCondensed matter physicsMineralogyMaterials science

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