Phase Transformations and Properties of Titanium Dioxide Systems

Titanium dioxide displays a rich array of structural forms, ranging from the well-known ambient polymorphs—anatase, rutile and brookite—to high-pressure and low-density variants. These polymorphs differ in the connectivity of TiO6 octahedra, leading to distinct optical, electronic and mechanical properties. Under varying temperature and pressure conditions, TiO2 undergoes transitions to phases such as columbite, baddeleyite and cotunnite, while nanoscale confinement and defect engineering introduce amorphous and low-density architectures. Point defects, especially oxygen vacancies and dopant atoms, modulate band gaps and charge carrier dynamics, underpinning applications in photocatalysis, photovoltaics, sensing and electrocatalysis. Recent advances in computational modelling and in situ characterisation have elucidated transformation pathways, stabilisation criteria and structure–property relationships across the phase diagram, guiding the design of TiO2-based functional materials for energy and environmental technologies.

Research from Nature Portfolio

Recent studies have uncovered novel low-density two-dimensional and hexagonal-cage phases assembled from TiO2 clusters, expanding the polymorphic spectrum beyond conventional anatase and rutile. Detailed density functional calculations paired with cluster-based self-assembly revealed stable architectures within a narrow energy window, highlighting potential for lightweight frameworks with unique optical gaps. Variable-temperature synchrotron X-ray powder diffraction has similarly advanced understanding of defect-mediated phase behaviour in anatase, rutile and mixed powders. Here, anisotropic thermal expansion serves as a probe for sub-surface oxygen vacancies and nitrogen dopant levels, and has led to the identification of a cubic titanium oxynitride emerging at elevated temperatures, which shifts absorption into the visible range and enhances photocatalytic performance.

Phase Transformations and Properties of Titanium Dioxide Systems publication trend

The graph below shows the total number of articles in phase transformations and properties of titanium dioxide systems across all publications each year (not limited to Nature Index journals).

Technical terms

Polymorph: A distinct crystal structure in which a compound can crystallise.

Anatase, Rutile, Brookite: The three common TiO2 polymorphs, differing in TiO6 octahedral connectivity and optical properties.

Oxygen vacancy: A point defect arising from a missing oxygen atom in the lattice, influencing electronic and optical behaviour.

Martensitic transformation: A diffusionless phase change driven by cooperative atomic shifts under stress or temperature.

Band gap: The energy difference between the valence and conduction bands, defining a material’s optical absorption edge.

Δ-learning potential: A machine-learning model calibrated against ab initio data to predict phase stabilities over wide conditions.

References

1. Low density phases of TiO2 by cluster self-assembly. Scientific Reports (2024).
2. Characterisation of oxygen defects and nitrogen impurities in TiO2 photocatalysts using variable-temperature X-ray powder diffraction. Nature Communications (2021).
3. High-pressure phase behaviors of titanium dioxide revealed by a Δ-learning potential. The Journal of Chemical Physics (2022).
4. Electronic structure characterization of TiO2-II with the α-PbO2 structure by electron-energy-loss-spectroscopy and comparison with anatase, brookite, and rutile. Journal of Solid State Chemistry (2023).