Diverse Interface Structures in TiO₂ (B)/Anatase Dual-Phase Nanofibers

The understanding on the interfaces between different polymorphs of nanosized TiO₂ from the perspective of crystallography has great theoretical value for the interface and property design and regulation. In this work, TiO₂ (B)/anatase dual-phase nanofibers containing different interface structures are investigated in detail. The X-ray diffraction (XRD) is first employed to illustrate the detailed phase evolution during the calcination under different temperatures. Four types of interfaces with different structures are further studied by transmission electron microscopy (TEM). Single crystal form induced different interfaces is confirmed, which is thought to be the universal conclusion in monoclinic crystal systems. Meanwhile, the other two interface structures in {100} single crystal form are also observed in the samples under higher temperature calcination. Invariant line strain calculation is carried out for the four interfaces. The calculated crystallographic features agree well with the observed results. Furthermore, taken [010]_TB//[001]_TA as the rotation axis, the orientation difference of the single crystal form induced interfaces is confirmed to be 72.5°, corresponding to the β angle of TiO₂ (B). The orientation relationships of the other two interfaces in {100} single crystal form can also be achieved by 7.5° and −4.5° rotation from the interface with the same single crystal form.