Interaction between dislocations and NiFe<inf>2</inf>O<inf>4</inf> precipitates in a NiO matrix

Dislocations have been introduced into NiO containing particles of NiFe2O4 by room temperature deformation. The interaction of the dislocations with the particles has been examined using weak-beam imaging in the TEM. The dislocations have a a 2〈011〉 Burgers vectors and {011} glide planes. By heating a TEM sample which contained spinel particles surrounded by dislocation loops, the effect of dislocations on the particle morphology could be studied. An individual dislocation loop can cause a cusp in the precipitate which can act as a "noose" around the particle causing it to shrink. Dislocations can act as preferential sites for spinel nucleation as was observed for different nucleation rates. For slow nucleation rates, nucleation only occurred at the dislocations while nucleation also occurred elsewhere for a larger nucleation rate. Spinel precipitates can grow at dislocation to form a stacking fault in the precipitate-perfect dislocations in NiO are only partial dislocations in the spinel. The position of the stacking fault indicates the location of the original nuclei. © 1992.