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(d)
(e)
Figure 7.64 Continued
less smooth and vitreous in luster, with a high degree of transparency. The prism
faces dominated over all other faces in all the crystals followed by pinacoidal and
dome faces. There is a clear-cut distinction in the morphology of these pyropho-
sphates. In most of the experiments, the entry of the selective dopants was con-
trolled in order to observe the morphological variations. The morphology of these
pyrophosphates varies from one to another, depending on the cations present.
To gain an understanding of the morphological variation with respect to the
growth conditions, it is essential to study particularly the role of the degree of
supersaturation, the concentration of water and Na 2 O in the system. NaHCo(P 2 O 7 )
and NaHZn(P 2 O 7 ) crystals were selected for such a systematic study, because these
compounds show a very well-developed morphology and are sensitive to such var-
iations. In fact, both these compounds show similar morphological variations.
Figure 7.64a
e shows how the morphology varies with the concentration of P 2 O 5 .
This is further represented in the schematic diagram of Figure 7.65 . The interfacial
angles for the representative pyrophosphates have been measured using a Leitz
phase-contrast microscope and these angles are shown in the schematic diagrams
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