The Prediction of Carbothermal Reduction Reaction Induced Ti₄O₇/Ti₅O₉ Interface Structures in Titanium Oxide Nanosystems

Abstract

The reduced titanium oxide (TinO2n‐1, 4 ≤ n ≤ 10) material system has attracted considerable attention due to their unique crystal structure and excellent electrical and chemical properties. Interface science and engineering play a very important role in both the synthesis or usage of such material, not only because the commonly observed multiphase coexistence phenomenon during the preparation process, but also due to the special physical and chemical properties brought by the heterogeneous interfaces. The lack of research on the interface structures as well as their influence on the properties seriously hinders the development of TinO2n‐1. In this work, crystallographic model is employed first to predict the crystallographic features of Ti5O9/Ti4O7 interface in titanium oxide nanosystems. The initial lattice correspondence is determined after fully considering the crystal symmetry and structures of Ti5O9 and Ti4O7. To verify the predicted results, Ti5O9/Ti4O7 nanocomposites are prepared through carbothermal reduction reaction, followed by detailed X‐ray diffraction and transmission electron microscopy characterizations. The observed orientation relationships between Ti5O9 and Ti4O7 are consistent with the predicted results, which confirm the application of crystallographic model in the phase transformation in which chemical reaction involved.

Phase transformation and interface crystallography between TiO2 and different TinO2n−1 phases

“…Generally speaking, it is necessary to first establish the corresponding parallel relationships between the close-packed planes (or near closepacked planes) and the close-packed directions (or near close-packed directions) located on the crystal planes for the parent and new phase, and further determine the third relationship perpendicular with the above two relationships. 25,56 This is because the shortest migration distance of atoms is along the close-packed direction on the close-packed plane during the phase transition. However, unlike crystals with simple structures such as FCC or BCC, it is difficult to determine specific close-packed planes and orientations in low-symmetry crystals due to relatively large differences in unit cell parameters and complex atomic arrangements.…”

“…By employing different types of reducing agents, TiO 2 will gradually transform to the Ti n O 2n−1 phase with different reduction degrees through a series of phase transitions. [24][25][26] During this process, TiO and TiO 2 layers are alternately arranged in the structure by means of TiO 6 octahedral recombination and shearing is generated accordingly. 27 That is, the Magneli phase Ti n O 2n−1 is formed, accompanied by dramatic changes in the crystal structure and formation of massive interfaces.…”

Formation mechanism of Ti4O7 phase prepared by carbothermal reduction reaction

“…26 Lei et al adopted the CRR method to prepare different Magnéli phases, and the products were composed of Ti 4 O 7 , Ti 5 O 9 , and TiO 2 that were indicated by the X-ray diffractions (XRD) patterns. 27 It is well-known that the purity of the products with single-phase is quite important and relating to the properties directly. Ti 4 O 7 exhibits the highest electrical conductivity among the titanium suboxides, and the existence of other suboxides impurities will dramatically decrease the overall electrical conductivity.…”

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

“…Concerning the multiple interface structures, the construction of different initial Bain strain matrix is quite important to interpret the diverse OR as well as the relationship between them in a certain material system. Basically, the parallel relationships between the close‐packed planes and close‐packed directions of the parent and new phase can be established first then followed by a third parallel relationship perpendicular with the above two directions . However, the appearance of diverse ORs normally implies lower crystal symmetry and complicated structure of both parent and new phase.…”