Crystal growth of fluorine-doped tin oxide structures with extraordinary morphology by the hydrothermal method and their electrical conductivity

In this work, fluorine-doped tin oxide (FTO) crystal structures with different morphology and the phase composition were synthesized by the hydrothermal method. It was shown that the controlled addition of NH4F to the initial solution leads to a change in the pH of the reaction mixture. Varying the pH of the initial mixture results in a change in the shape of growing crystals from a flower-like to a prismatic and phase transformation of the resulting crystal structures. Flower-like FTO structures obtained at a mass ratio of F/SnO2 = 0.05 show the highest conductivity in the synthesized series. A detailed microstructural analysis indicates that these structured particles consist of primary nanocrystals that are misoriented and have different preferential growth directions. It is assumed that an enhancement in the conductivity can be due to the synergistic effect of defects formed during the spontaneous growth of FTO nanocrystals under hydrothermal conditions and their local interaction.