In addition, the peaks at 25.4° (2θ) become gradually
sharp, with increasing calcination temperature from 350 to
750 °C, implying that TiO2 nanoparticles grow large and
crystals trend to perfect anatase. Generally, the full width at
half maximum of XRD peak is related to the particle size of
crystal materials. The larger the width, the smaller the
crystalline size is. The mean sizes of a single crystallite can be
estimated from the full-width at half-maxima of XRD peaks
by using Scherrer’s formula[27]. The average sizes of pure TiO2
powder and the nanocomposites calcinated at different
temperatures are listed in Table 2. It is evident that the crystal
size of pure TiO2 is larger than that in the nanocomposites
calcined at the same temperature. The crystal size of TiO2 in
the nanocomposites increases with increasing calcination
temperatures, suggesting that high temperature leads to TiO2
crystal growth without transformation of crystal phase. The
result indicates that as-deposited anatase TiO2 nanoparticles
are stable.