The IR spectral frequency of uncalcined hydrogels and calcined powders of all the compositions are presented in
Table 2 and the detailed IR spectra of the A15Z powder calcined at different temperatures have been shown in Fig. 2.
All the gels and calcined samples exhibited –OH stretching vibration in the frequency range of 3136–3857 cm1
. The reduced reflectance and bond depth of the gel powder could be ascribed to the non-crystalline nature of the material [17]. The number of peaks for –OH stretching vibration in the Al2O3–ZrO2 powder increases with an increase in the ZrO2
content. The increased IR interaction probably reflects a gradual change in the composition and heterogeneity in the
bond as well as a switchover from a homogenous single phase structure to a homogenous two phase structure intuitive. The frequency of different vibrational modes of Al–OH and/or Zr–OH including the bending and stretching modes are
altered due to change in the charge distribution among molecules. This altered frequency of vibration in turn causes a
change in the electrical dipole moment of the original species. The charge distribution around each Al–OH and/or Zr–OH and associated vibration is influenced by the charge on its neighboring species. Hence, the continuum vibration of the
matrix is responsible for the change in dipole moment and establishment of an electric field of the composite powder. The
increased cationic charge in the alumina–zirconia composite powder due to the introduction of Zr4+ interacts strongly with
the polar inner hydroxyl groups. This interaction probably results in the reduction of vibrational dipole moment in bending
thereby creating a greater force of attraction (antisymmetric coupling) on the stretching vibration.