Geoscience Reference
In-Depth Information
8
Hydrothermal Synthesis and Crystal
Growth of Fluorides, Sulfides,
Tungstates, Molybdates, and
Related Compounds (Coordinated
Complex Crystals, Part II)
8.1 Introduction
The hydrothermal synthesis of complex coordinated compounds covers a vast
group of compounds. In Chapter 7, which deals with Part I of these complexes, we
covered silicates, germanates, phosphates, vanadates, and borates. Here we deal
with fluorides, sulfides, tungstates, titanates, molybdates, tantalates, neobates, sele-
nides, and related compounds.
The synthesis of these compounds did not carry much geological significance in
the past; hence, their synthesis began in the middle of the twentieth century.
However, the interest was purely academic. Today, these compounds have a great
technological significance. Although the synthesis of these compounds is being
studied extensively worldwide, interest is more confined to the nanosize crystals
rather than bulk single crystals growth. Some of these coordinated complexes with
reductions in the size and the establishment of core-shell structures carry special
characteristics useful as sensors, quantum dots, imagers, semiconductors over a
wide band gap region, and so on. Since the publication of the first edition of this
topic, publications are seldom found on the bulk single crystal growth of these com-
plex coordinated compounds, as interest is mainly confined to the nanosize crystals,
which are discussed separately in Chapter 10.
8.2 Fluorides
Fluorides form a large group of inorganic compounds; from the simplest to the
most complicated types. In addition, we have fluorophosphates, fluorocarbonates,
fluoroarsenates, oxyfluorides, and so on. These compounds contain a great variety
of cations of the elements from groups 1, 2, 3, and 4 of the Periodic Table. For
simple fluorides like the AF type (where A
Li, Na, K, Rb, Cs), the optimum
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