A TRANSMISSION ELECTRON-MICROSCOPY STUDY OF LATTICE-DEFECTS IN MN3O4 HAUSMANNITE

A theoretical survey of lattice defects including transformation twins due to a structural transformation is presented for Mn3O4 hausmannite . Room-temperature transmission electron microscopy observations of sy nthetic samples reveals that accommodation twins are present, associat ed with the structural transition. Two types of {112} twin wall were f ound: coherent and incoherent twin walls, in agreement with theoretica l predictions. Two types of undissociated perfect dislocation with Bur gers vector [100] and 1/2[111] were identified, both corresponding to 1/2[110] Burgers vectors of perfect dislocations in the parent high-te mperature spinel phase. Dislocations interact strongly with twin bound aries.