Solvothermal synthesis denotes chemical transformation in a solvent contained within a closed vessel at a temperature above the solvent’s normal boiling point, so that autogenous or externally imposed pressure maintains a condensed reaction medium. The solvent is an active physicochemical variable: its polarity, proticity, coordinating ability, viscosity, and supercritical or subcritical state influence precursor solubility, hydrolysis, condensation, transport, and nucleation ^[1]. Temperature, pressure, fill fraction, precursor concentration, and mineralizers jointly define the reaction domain. Hydrothermal synthesis is the aqueous subset; solvothermal synthesis is broader and includes nonaqueous solvents ^[2]. The concept is not synonymous with ordinary reflux, because the sealed system permits temperatures and pressures inaccessible at the solvent’s atmospheric boiling point, and it is distinct from dry solid-state reaction because molecular transport and chemical speciation occur in a fluid medium. Products may precipitate or crystallize in situ as supersaturation develops.