Solvothermal synthesis, also referred to as autoclave synthesis, includes the various techniques of crystallizing substances from high-temperature solutions at high vapor pressures. 

The hydrothermal method can be used for the synthesis of single crystals that depends on the solubility of minerals in hot water under high pressure. The precursor solution, a mixture of precursors and solvent, is loaded in a Teflon tube, which is applied to an apparatus consisting of a steel pressure vessel, the so-called autoclave. A temperature gradient is maintained between the opposite ends of the growth chamber. At the hotter end, the precursor can dissolves in the solution, while at the cooler end it is deposited on a seed crystal, growing the desired crystal.

The method is particularly suitable for the growth of large good-quality crystals while maintaining control over their composition. The autoclaves which are used in the working group Mathur can be used up to 230°C and 10 bar.