well as 1401 cm-1 (δCH) in the PbWO4 microspheres can be
attributed to the characteristic frequencies of residual organic
materials. The absorption band at 1065 cm-1 is assigned to the
SO32- group,24 indicating the incorporation of SDS into microspheres. The thermal behavior of PbWO4 microspheres was
analyzed by TG technique (Figure 5b). The results showed that
the PbWO4 microspheres consisted of nanoparticles and contained little water. The mass loss between 200 and 700 °C was
ascribed to the decomposition and desorption of residual organic
materials. The amount of these soft materials in the microspheres
is about 5.0 wt %.
A plausible formation process of microspheres was proposed.
First, when Pb2+ and C3H2O7 2- are mixed together, Pb-
(C3H2O7) complex will form and precipitates. Then, the addition
of WO
24
- resulted in the formation of amorphous PbWO4 by
competing for Pb2+ with C3H2O7 2-. Because Pb(C3H2O7) is a