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This study used ultrasound irradiation to fabricate Zn 2+ -doped £-Ga 2 O 3 nanoparticles (NPs) from ZnGa alloy at near-room temperature (60 °C). The Zn 2+ -doped £-Ga 2 O 3 NPs were obtained at 60 °C after two steps of ultrasound irradiation (miniaturization and oxidation of ZnGa alloy). The specific surface area of Zn 2+ -doped £-Ga 2 O 3 NPs with a zinc content of 4 at.% was 90.4 m 2 /g. The oxidation behavior of ZnGa liquid alloy significantly differed from that of liquid Ga. X-ray photoelectron spectroscopy spectrum and lattice constant of Zn 2+ -doped £-Ga 2 O 3 confirmed Zn 2+ -doping into the £-Ga 2 O 3 crystal structure. By annealing at 900 °C, the obtained Zn 2+ -doped £-Ga 2 O 3 did not transform to Zn 2+ -doped ¢-Ga 2 O 3 but to the mixed phase of ¢-Ga 2 O 3 and ZnGa 2 O 4 . The results indicate that Zn 2+ cations, with larger ionic radii than Ga 3+ cations, are more difficult to be introduced into the ¢-Ga 2 O 3 crystal lattice. Thus, this ultrasound process can potentially synthesize various metal cations-doped £-Ga 2 O 3 NPs without using high temperatures and pressures.

This paper investigated the effect of two-step ultrasound irradiation (miniaturization and oxidation) on various gallium-based liquefied alloys in ethanol and hydrazine monohydrate at 60 °C. The miniaturization and oxidation behavior of the liquefied alloys were analyzed. In the Ga-based alloy system, the miniaturization process was not as efficient as that of pure gallium due to changes in corrosive properties, surface tension, and viscosity caused by the addition of other metals. In the oxidation step, nanosized crystal grains were abundantly generated at the initial stage, and metal-doped £-Ga 2 O 3 was finally obtained in the GaAl and GaMg systems. However, in the GaAg system, the alloy's oxidation rate was slow, and Ag-doped £-Ga 2 O 3 was not obtained. These results suggest that the redox potential of added metals significantly affects the oxidation behavior. By utilizing this phenomenon, it is possible to synthesize £-Ga 2 O 3 nanoparticles with controlled composition and morphology.

Porous gallium oxide films were tried to synthesize at low temperatures. Ga nanoparticle dispersions were synthesized using ultrasound irradiation in 2-propanol and two films methods were considered. In the case of the spray coating of Ga nanoparticle dispersions and treatment with hydrazine vapor, Ga films were obtained. In the case of depositing Ga nanoparticles on a cover glass and aging them in hydrazine solution at a refrigerator temperature, porous £-Ga 2 O 3 film was synthesized. This new process of low-temperature aging in a refrigerator using hydrazine solution allows synthesizing porous £-Ga 2 O 3 film. Generally, the synthesis of oxide ceramics requires high-temperature processing, but this method allows oxidation at low temperatures, such as refrigerator temperatures, making it an energy-efficient process.