Geoscience Reference
In-Depth Information
Although there are thousands of research publications on hydrothermal research,
so far, the most comprehensive works are limited to reviews and edited topics.
No topics have been available until the publication of this work. In connection with
the hydrothermal technique for crystal growth and materials processing, the topics
and reviews listed in
Table 1.1
are very useful.
We have made a very sincere effort to collect a more-or-less complete list of pub-
lications related to the field of hydrothermal technology, especially with a higher
reliability in the last decade. Therefore, it is interesting to discuss briefly the statis-
tics of this field of research.
Figure 1.12a
shows the number of publications year-
wise from 1989 up to 1999,
Figure 1.12b
and shows the number of publications
year-wise from 2000 up to mid-2011, and this number is increasing steadily with the
entry of scientists from other branches of science. The preparative chemists and
ceramists have dominated this field, particularly with the recent advances in the
advanced materials and electronic ceramics. It is interesting to note that the hydro-
thermal technique of material synthesis, although began in the previous century, has
gained its momentum during the postwar period. Prior to that, the majority of the
compounds synthesized under hydrothermal conditions were essentially natural ana-
logues, as the main thrust was on the study of the origin of rocks, minerals, and ores
through laboratory simulations (
Figure 1.13a,b
shows the number of papers on
hydrot
hermal research in materials science during 1989-2011).
With the availability of the improved equipment and also with the knowledge
on the preparative chemistry routes to synthesize many inorganic compounds, with
or without natural analogues under hydrothermal conditions, the popularity of the
technique grew fast. Today, the number of compounds without any natural ana-
logue synthesized under hydrothermal conditions is more than the number of com-
pounds with natural analogues synthesized. With the advent of new mineralizers, a
wide variety of organic and inorganic compounds hitherto unknown are being pre-
pared by the hydrothermal technique. The technique is being popularly used for the
crystallization of materials, crystal growth, materials processing, thin film prepara-
tion, and so on. As is evident from the synthesis of silicates, phosphates, and oxides
followed by the ceramics are very popular materials being obtained under hydro-
thermal conditions. The popularity of this field is probably connected with the bet-
ter understanding of the hydrothermal solution chemistry and the effective use of
several new mineralizers which have virtually changed the scenario, particularly
with reference to the pressure and the temperature conditions of synthesis of mate-
rials which were obtained under very HPHT conditions. For instance, rare earth
tungstates, rare earth silicates, and so on are being obtained under mild hydrother-
mal conditions
[114]
.
Hydrothermal research had its origin in Europe and later spread its activity to
North America during the early twentieth century. Hydrothermal research in Asia
began in the 1920s in Japan. Today, China and Japan have emerged as leaders in
this field of research on a par with the United States. However, hydrothermal
research is becoming quite popular in several other countries, particularly in the
last four decades. The countries engaged in hydrothermal research are listed below
in alphabetical order: Australia, Belgium, Brazil, Bulgaria, Chile, China, Canada,
