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

Abstract

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.

Study on the evolution from α-GaOOH to α-Ga2O3 and solar-blind detection behavior of an α-GaOOH/α-Ga2O3 heterojunction

“…It can also be confirmed that α-GaOOH is completely transformed into α-Ga 2 O 3 after annealing at 370 °C for 4 h due to the disappearance of the vibration related to the OH bond in the transition process. The above phenomenon directly proves the dehydroxylation process of α-GaOOH to α-Ga 2 O 3 , as shown in the following reaction equation: 24 2GaOOH → Ga 2 O 3 + H 2 OXRD and FT-IR tests both reflect the coexistence of α-GaOOH and α-Ga 2 O 3 at a certain temperature. Studying this transition state will help the understanding of the transformation from α-GaOOH to α-Ga 2 O 3 .…”

Fabrication of vertical orthorhombic/hexagonal tungsten oxide phase junction with high photocatalytic performance

“…Various kinds of strategies have been proposed to improve separation and transfer efficiency of the photogenerated charges, among which fabrication of phase junctions is an effective approach. [9][10][11][12] The phase junctions in polymorph semiconductors, such as the anatase/rutile phase junction in TiO 2 [2,[13][14][15][16][17][18][19][20] and α/β phase junction in Ga 2 O 3 [21][22][23][24][25] have been widely investigated. This kind of phase junction constructed by the different phases of the same semiconductor has attracted much attention due to its simplicity, controllability and great photocatalytic activity.…”

One-step solvothermal synthesis and growth mechanism of well-crystallized β-Ga2O3 nanoparticles in isopropanol

“…These results confirm that the crystalline phase transition from γ-Ga 2 O 3 to β-Ga 2 O 3 occurred within 1440 min at 400°C. As discussed in the Introduction, the calcination of GaOOH, α-Ga 2 O 3 , or γ-Ga 2 O 3 at 700°C or above in air produces β-Ga 2 O 3 particles, 8,13,14,[17][18][19]26,28,35,36 which is the most stable phase. The detailed mechanism of the phase transition from γ-Ga 2 O 3 to β-Ga 2 O 3 has been reported recently.…”

“…22,23 Due to the wide application prospect of β-Ga 2 O 3 , its synthesis in the form of nanoparticles, nanorods, and thinfilms has received intensive research attention. Thus, for the synthesis of β-Ga 2 O 3 nanoparticles, a number of liquid processes based on the sol-gel method, 8,12,19,24 hydrothermal synthesis, 14,25,26 solvothermal synthesis, 18,[27][28][29] sonochemical method, 30 and solution combustion 31 were proposed. In most cases, the liquid processes involve the preparation of intermediate products such as GaOOH and γ-Ga 2 O 3 nanoparticles, which are then converted to β-Ga 2 O 3 nanoparticles by calcination at a temperature of 700°C or higher in air.…”