Disadvantages : The limitations vary depending upon the technique:

Synthesis from the melt – Many compounds melt incongruently (they decompose upon melting) so that synthesis from the melt is not possible. Reactions with the crucible can also be problematic.

Chemical Transport – Generally limited to crystal growth and purification of compounds, which have already been synthesized using another technique.

Molten Salt Fluxes – Impurities can result from incorporation of the molten salt in your product.

Hydrothermal – Some compounds are not soluble, even in superheated water. Products can be rather inhomogenous .

Solid State Metathesis – Suffers from incomplete conversion to products, and its applicability for synthesis of complex materials is unclear.