A Real Time Observation of Phase Transition of Anatase TiO2 Nanotubes Into Rutile Nanoparticles by In-Situ Joule Heating Inside Transmission Electron Microscope

We report the in situ Joule heating induced phase transformation of anatase TiO2 nanotubes into rutile nanoparticles inside a high-resolution transmission electron microscope (TEM) equipped with a scanning tunneling microscopy (STM) probe. Under a bias heating of 10 V, the anatase TiO2 nanotube breaks into ultrafine anatase nanoparticles of average size between 5-10 nm. On further increasing the bias voltage to 20 V, the nanoclusters of anatase particles become prone to a solid state reaction and are grown into stable rutile nanoparticles of size ranging between 20-25 nm. The formation of rutile nanoparticles was confirmed by the observation of diffraction pattern and high resolution imaging of these particles, which corresponds to the tetragonal TiO2 rutile phase (a = 4.59 angstrom, c = 2.95 angstrom, P4(2)/mnm).