. Results
XRD patterns of the as-synthesized samples are shown Fig. 1. The
broad halo diffraction peaks indicate that the as-synthesized samples
are amorphous in nature.
FTIR spectra of the glass samples are depicted in Fig. 2a. There are
mainly three absorbance bands as labeled by the vertical lines in the figure.
The band at around 1020 cm−1 is assigned to the asymmetrical
stretching vibrations of Si\O\Si bonds in silicon-oxygen tetrahedra
[17]. It significantly shifts to lower wavenumbers with the increase of
ZnO. The band at 780 cm−1 can be assigned to the bending vibrations
of Si\O\Si bonds [18]. From Fig. 2b, it can be seen that this bandslightly shifts to higher wavenumbers and becomes less apparent with
the increase of ZnO. There is a big absorbance band at 455 cm−1 and
small absorbance bands at around 470–520 cm−1
. These bands are correlated
with the bending vibrations of Si\O\Si and Si\O\Al bonds
[19]. There is no big difference among these bands with the increase
of ZnO.