Size effects on the structure and phase transition behavior of baddeleyite TiO2

High-pressure structural transitions in nanocrystalline systems are of significant interest as models of first-order phase transitions. We demonstrate size-induced lattice expansion and significant atomic rearrangements in the crystal structure of nanocrystalline high-pressure baddeleyite-TiO2. The α-PbO2 structured TiO2 recovered after dozens of pressure cycles in the α-PbO2-baddeleyite pressure field displayed elongate 25–35 nm crystallites, compared to starting 34-nm anatase crystallites, suggesting crystallite coherency across anatase, baddeleyite, and α-PbO2 structures and ‘single structural domain’ behavior of the nanocrystalline system.