To further ascertain the presence of CAO, it was characterized by
FTIR and its spectrum is shown in Fig. 2(a). All the peaks can be
indexed to the absorption of CueO stretching vibration at 550 cm1,
and AleO stretching vibration of distorted AlO6 octahedrons at
760 cm1, in accordance with the previous reports [8,11]. In this
research, the OeCueO antisymmetric vibration was not detected.
The analysis confirmed that the CAO product was not contaminated
with any starting materials because the acetate (CH3COO) and
nitrate (NO3
) functional groups were not detected. A certain existence
of the CAO crystal was also evaluated by Raman analysis. The
Raman spectrum of CAO crystal (Fig. 2(b)) presents two Raman
active modes of Eg and A1g at 419 and 763 cm1, respectively. These
Raman shifts are in good accordance with those obtained by
Pellicer-Porres et al. [16]. In this study, the CAO product was
composed of only CAO phase, synthesized by the direct microwave
heating method.