Phase Evolution of Ga2O3 Produced from Morphology‐Controllable α‐GaOOH Nanocrystals

Fine powders of GaOOH nanocrystals are synthesized via a facile hydrolysis process through the solution–solution interface reactions of anhydrous GaCl₃ and distilled water followed by subsequent solvothermal treatment at mild conditions. Well‐faceted α‐GaOOH hexagonal prism‐like nanorods are prepared through solvothermal treatment at 180°C with CTAB as the morphology controlling surfactant. Ga₂O₃ nanocrystals are fabricated via the pyrolysis of α‐GaOOH hexagonal prism‐like nanostructures at temperatures above 410°C. A peculiar back‐transformation from β‐Ga₂O₃ to α‐Ga₂O₃ has been observed to occur between about 557°C and 719°C, which is considered to be responsible for the coexistence of the two phases. The phase transformation mechanisms of Ga₂O₃ at elevated temperatures, as well as the possible transformation route, have been postulated from a thermodynamic point of view.