Defect generation of anatase nanocondensates via coalescence and transformation from dense fluorite-type TiO2

Abstract

The anatase nanocondensates produced by energetic pulse laser ablation on Ti target under oxygen background gas have been observed by transmission electron microscopy. They were found to coalesce in approximately parallel orientation on the (001) plane to form dislocations and in twin orientation on the (112) plane to form faulty and twinned crystals. The anatase phase (denoted as a) was also derived from the dense fluorite-type (denoted as f) condensates by a martensitic-type transformation to form twin variants following the crystallographic relationship ⟨001⟩f‖[100]a with a habit plane close to {100}f‖(001)a for a beneficial lower interfacial strain energy. The f-a transformation route of TiO2 can be rationalized by a metastable phase change in terms of the intersection of the internal energy versus cell volume curves of the polymorphs.