High pressures and chemical reactivity: an approach to the synthesis of novel materials

In material synthesis, high pressures are characterized by different factors: the weak conveyed energy compared to the temperature; the negative V value (if V is the volume difference between the final unit-cell volume of the resulting material and the sum of the unit-cell volumes of the precursors); the 'in situ' improvement of the chemical reactivity inducing rapid reaction kinetics (such an improvement being observed in particular in the presence of a liquid phase as solvothermal processes). In addition, the reaction mechanisms and the chemical reactivity of the precursors can play an important role in high-pressure synthesis. Consequently, in order to develop new high-pressure research domains involving novel materials, careful selection of either the reaction route or the chemical nature of precursors appears as a fruitful approach for decreasing the pressure and temperature conditions required for the synthesis. In particular, such an approach is important for the synthesis of novel materials characterized by specific physical properties (hardness, magnetic or electrical properties, etc.) able to lead to industrial developments.