Differences in the Defect Structures of the Reaction Fronts of Solid State Reactions within Interface- and Diffusion-Controlled Reaction Regimes

1997 ◽  
Vol 143-147 ◽  
pp. 649-654 ◽  
Author(s):  
Heino Sieber ◽  
D. Hesse ◽  
P. Werner ◽  
Stephan Senz
Keyword(s):  
Solid State ◽  
Solid State Reactions ◽  
Defect Structures ◽  
Reaction Fronts ◽  
Diffusion Controlled ◽  
And Diffusion ◽  
Diffusion Controlled Reaction

The Structure of Spinel/Oxide Reaction Fronts During Spinel-Forming Solid State Reactions

1994 ◽  
Vol 357 ◽  
Author(s):  
D. Hesse ◽  
R. Scholz ◽  
S. Senz ◽  
H. Sieber ◽  
P. Werner ◽  
...  
Keyword(s):  
Solid State ◽  
Reaction Front ◽  
Lattice Misfit ◽  
Solid State Reactions ◽  
Interface Plane ◽  
Misfit Dislocations ◽  
Spinel Oxide ◽  
Oxygen Sublattice ◽  
Cross Sectional ◽  
Reaction Fronts

AbstractA series of spinels were grown by topotaxial solid state reaction on MgO(001) and sapphire(11.2) substrates. The structure of the various spinel/oxide reaction fronts was investigated by cross-sectional high resolution electron microscopy and other methods. While for extremely low misfit the reaction front is completely coherent, different interfacial defects form in other cases, depending on sign and amount of the spinel/oxide lattice misfit. For a large positive misfit, a network of misfit dislocations occured all running along <100<, with Burgers vectors of types a/2[101] and a/2[011] pointing out of the interface. The perpendicular Burgers vector component along [001] permits these dislocations to glide in order to cope with the advancing reaction front, avoiding kinetically unfavourable climb processes. The latter have, however, been observed in negative misfit, where the interfacial dislocations run along <110>, with their Burgers vectors lying in the interface plane. At the sapphire/MgAl2O4 front the structure is completely different. Here the h.c.p.-type oxygen sublattice of sapphire is reconstructed into the f.c.c-type oxygen sublattice of the spinel, which requires a tilt of the MgAl2O4 lattice and the formation of interfacial ledges.

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