Fig. 3(a–c) shows the SEM micrographs used to study the microstructures
of the CaSiO3:Eu3+, Bi3+ powders. The morphological
characteristics of the prepared powders are strongly dependent
on the heat and gases generated during the complex decomposition
in combustion method. While the heat released is an important
factor for crystal growth. The preparation of tiny particles is
done through the large amount of gases. An inspection of the morphology
of the synthesized powder samples Calcined 950 C for
3 h, reveals that the phosphor powders are characterized by flakes
up to 5 lm. During the combustion process, the surface of the powder
samples shows voids and pores formed by the escaping gases.
The wide particle-size distribution as well as irregular shapes of
the particles is probably due to the non-uniform distribution of
temperature and mass flow in the combustion wave [15]. Fig. 4
depicts the TEM images of CaSiO3:Eu0.04Bi0.03 particles, which are
mixture of irregular shaped aggregates and nearly spherical shaped
particles having average size in the range of 30–40 nm.
This agglomeration of particles is the typical nature of combustion
synthesis and is consistent with the SEM results.
The FT-IR spectra of CaSiO3:Eu3+, Bi3+ phosphors Calcined 950 C
for 3 h are shown in.
Fig. 5(a)–(c). The spectroscopic analysis confirmed that the IR
peaks at 465, 680 and 964 cm1 are due to CaSiO3 [16,17]. It is
observed that the broad band from 840–1240 cm1 is due to asymmetric
stretching vibration of Si–O–Si bond and stretching vibrations
of terminal Si–O bonds. The peaks at 434–564 cm1 and
680 cm1 are the characteristic stretching vibrations of Si–O–Si
bridges. The sharp peak corresponding to 680 cm1 can be ascribed
to Si–O bond, which exists in the form of SiO32. It can be noticed
that there is no change in the position or intensity of absorption
bands for the Ca0.96xEu0.04BixSiO3 (x = 0.01, 0.03 and 0.05) which
confirms that the dew-point has not altered its phase and crystallinity.
These results are consistent with those of PXRD results.