Geoscience Reference
In-Depth Information
32
×
10
2
Coexistence curve
H
2
O
(g)
+ H
2
O
(I)
28
24
90%
80%
70%
60%
50%
20
40%
16
30%
Critical fill
12
20%
8
10%
4
Critical temperature
0
0
100
200
300
400
Temperature (°C)
500
600
700
800
900 1000
Figure 2.6 PVT diagram of water
[47]
.
Keyes
[46]
are the most significant ones. Later, Kennedy
[54]
oriented his famous
PVT data on water. Kennedy's diagram is shown in
Figure 2.6
.
Hitherto, the hydrothermal researchers were quite satisfied with the synthesis of
inorganic compounds that resemble or are similar to natural minerals. They did not
bother much about the size of the crystals obtained. The growth rate was extremely
low because of the lack of accurate knowledge on the proper solvent, and with
such slow growth rates, the hydrothermal research was less promising. Only a few
people were engaged in this research studying the phase relations in various sys-
tems including that of water, and the interest was mainly on Geoscience. However,
when Brazil imposed an embargo on the supply of high-purity quartz which was a
strategic material for the telecommunications purpose during World War II, hydro-
thermal researchers began to think seriously about the growth rate of crystals. At
that time, Brazil was the only source country in the world for electronic grade natu-
ral quartz, and even today, the situation is the same. Thus, the crisis, owing to the
shortage of pure quartz, forced many researchers to jump into the field of hydro-
thermal research with a sole objective of growing large-size single crystals of
quartz. Many countries like the United States of America, United Kingdom,
Germany, and the erstwhile Soviet Union were in the field and the success
achieved was immense. Therefore, the period from the late 1930s to 1940s is
referred to as the “golden period” in the hydrothermal research, not only because
of the enhanced research activity, but also because of the many new discoveries
with reference to autoclave designs and other important technological materials.
The authors feel that it is highly appropriate to discuss briefly the historical
contribution made by the German hydrothermal researchers with reference to the
increased growth rate and growth of large-size single crystals of quartz. In contrast
