CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

ethylene glycol moiety (stabilizing ligand). In DTA pattern mainly a sharp exothermic peak
centered at 600°C was observed which is attributed to the phase transformation from
hexagonal BiPO to monoclinic BiPO .
4 4
Weigth loss (%)
0 TG
DTA
-2
-4
-6
0.4
0.2
0.0
-0.2
-0.4
-0.6
Heat Flow (µV)
-8
-0.8
200 400 600 800 1000
Temperature (°C)
Fig.77. TG-DTA pattern of BiPO sample prepared at room temperature.
4
In order to understand structural changes occurring during the synthesis of BiPO 4
nanomaterials at different temperature, FT-IR spectra were recorded for these samples
(Fig.78). The BiPO 4 nanomaterials prepared at room temperature and 100°C show similar
spectra with sharp peaks at 539 and 600 cm -1 together with broad bands centered around 1000
cm -1 and 3500 cm -1 (3500 cm -1 band is not shown). The strong band centered at 1000 cm -1 is
due to υ 3 stretching vibration of the PO tetrahedra and the peaks at 600 and 539 cm -1
4
correspond to δ(0-P-O) and v (P0 4 4), respectively [227]. Samples prepared at 125 and 185°C
show similar spectra except splitting of peaks corresponding PO 4 stretching vibrations. The
fine structure of the bands corresponding to PO 4 vibrations has been assigned to the reduction
of the crystal symmetry from pseudo T to C d 1. In order to check, whether the variation in
reaction temperature and crystalline phase has any effect on the particle size and morphology
of BiPO , detailed TEM studies were carried out. Figure 79 shows the TEM images of BiPO
4 4
135