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Titanium oxide compounds TiO,Ti2O3, and TiO2 with a considerable extent of nonstoichiometry were fabricated by pulsed laser ablation in water and characterized by X-ray/electron diffraction, X-ray photoelectron spectroscopy and electron energy loss spectroscopy. The titanium oxides were found to occur as nanoparticle aggregates with a predominant 3+ charge and amorphous microtubes when fabricated under an average power density of ca. 1 × 108W/cm2 and 1011W/cm2, respectively followed by dwelling in water. The crystalline colloidal particles have a relatively high content of Ti2+ and hence a lower minimum band gap of 3.4 eV in comparison with 5.2 eV for the amorphous state. The protonation on both crystalline and amorphous phase caused defects, mainly titanium rather than oxygen vacancies and charge and/or volume-compensating defects. The hydrophilic nature and presumably varied extent of undercoordination at the free surface of the amorphous lamellae accounts for their rolling as tubes at water/air and water/glass interfaces. The nonstoichiometric titania thus fabricated have potential optoelectronic and catalytic applications in UV–visible range and shed light on the Ti charge and phase behavior of titania-water binary in natural shock occurrence.

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Ferroelectric twin domains resulting from the cubic (c) to tetragonal (t) phase transformation at the Curie point TC≈130°C in pressureless‐sintered BaTiO3 ceramics, using TiO2‐excess powder, have been investigated using scanning and transmission electron microscopy. Both 90° and 180° domains were identified by spot splitting along characteristic crystallographic directions in the selected‐area diffraction patterns and/or from the shape of domain boundaries. Lamellar domains were found predominantly with the 90° types. The 180° domain boundaries mostly appeared wavy in shape, while the 90° ones, having sharpened ends, attained a dagger shape. Failure of Friedel's law in the non‐centrosymmetric t‐BaTiO3 was adopted to validate the existence of the 180° domains. The 90° domains with boundaries lying in are reflection–inversion twins, and the 180° domains lying in {100)t and }220)t are inversion twins. Convergent‐beam electron diffraction was performed to ensure that changing of the polar direction [001]t across the 90° and the 180° domain boundaries was consistent with the domain type. It was also used to confirm whether the 180°‐type walls are inversion domain boundaries produced by the loss of an inversion center when the cubic phase transforms into tetragonal symmetry. The formation of such ferroelectric domains is discussed with reference to the crystal symmetry reduction from (c‐phase) to P4mm (t‐phase) with a loss of mirror plane (m) and roto‐inversion axis upon c→t phase transformation.