Solvothermal processes can be described as the reaction or the decomposition of precursor(s) in presence of a solvent in a close system at a temperature higher than the solvent boiling point. Consequently pressure parameter is involved. Such processes are mainly managed by two sets of parameters: (i) thermodynamical parameters and (ii) chemical parameters.
Solvothermal processes concern either supercritical or subcritical conditions, -homogeneous or heterogeneous systems, and thermodynamical parameters (P and T) play an important role. The main interest of solvothermal reactions is the improvement of the chemical reactivity, and in such a case the nature of the reagents and the physico-chemical properties of the solvent are important.
For the last 20 years, solvothermal processes have been developed in different research areas, such as:
- synthesis of new compounds (including in particular hybride systems),
- crystal growth of functional materials,
- preparation of nanocrystallites with well defined size and morphology,
- deposition of thin films,
- sintering in mild temperature conditions.
In particular, solvothermal reactions involve nitrides and derived materials either for preparing new compositions or shaping functional nitrides (single crystals, nanoparticles…).
In a first approach the synthesis of nitrides using solvothermal reactions will be described versus the nature of the precursors and the composition of the solvent. The nitriding process will be analyzed versus the chemical species, in particular N3−, N3−…Different illustrations will be described (transition metal nitrides, light elements-based nitrides…).
The second part will be devoted to the development of solvothermal processes for the preparation of single crystals or nanocrystallites.
As a conclusion, the potential developments of solvothermal nitriding processes either in basic research or industrial applications will be discussed.