Special grain boundaries of anatase nanocondensates by oriented attachment

Anatase nanocondensates with a 1-D commensurate superstructure as prepared by the pulsed laser ablation of Ti in tetraethyl orthosilicate were identified by transmission electron microscopy to have special grain boundaries, i.e. symmetrical [100] tilt boundaries with (001) or (01) interfaces and an asymmetrical [10] tilt boundary with a (001)/(11) heterointerface. The [100] tilt boundaries are in fact due to basal twinning with a coherent (001) and a semi-coherent (01) interface, respectively, both following the Burgers vector = 1/2[00] + 1/4[00]. The (001)/(11) heterointerface is decorated with {101} ledges, both having a primitive coincidence site lattice for fair lattice coherency. These special grain boundaries can be rationalized by the (hkl)-specific rotation/coalescence of the crystalline nanocondensates.