Hydrothermal synthesis includes the various techniques of crystallizing substances from high-temperature aqueous solutions at high vapor pressures; also termed "hydrothermal method". The term "hydrothermal" is of geologic origin. Geochemists and mineralogists have studied hydrothermal phase equilibria since the beginning of the twentieth century. George W. Morey at the Carnegie Institution and later, Percy W. Bridgman at Harvard University did much of the work to lay the foundations necessary to containment of reactive media in the temperature and pressure range where most of the hydrothermal work is conducted.
A synthetic quartz crystal grown by the hydrothermal method
Synthetic quartz crystals produced in an autoclave at Western Electric's pilot hydrothermal quartz plant (1959)
In materials science, a single crystal is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries. The absence of the defects associated with grain boundaries can give monocrystals unique properties, particularly mechanical, optical and electrical, which can also be anisotropic, depending on the type of crystallographic structure. These properties, in addition to making some gems precious, are industrially used in technological applications, especially in optics and electronics.
A single-crystal quartz bar grown by the hydrothermal method
A high-purity (99.999 %) tantalum single crystal, made by the floating zone process, some single crystalline fragments of tantalum, and a high-purity (99.99% = 4N) 1 cm3 tantalum cube for comparison. This photo was taken by Alchemist-hp.
Fluorescence of (9H-carbazol-9-yl)(4-chlorophenyl)methanone single crystal.
A huge KDP, potassium dihydrogen phosphate, crystal grown from a seed crystal in a supersaturated aqueous solution at LLNL which is to be cut into slices and used on the National Ignition Facility for frequency doubling and tripling.