Near-room temperature synthesis of Zn²⁺-doped γ-Ga₂O₃ nanoparticles via direct oxidation of Zn–Ga alloy by ultrasound

Abstract

This study used ultrasound irradiation to fabricate Zn²⁺-doped γ-Ga₂O₃ nanoparticles (NPs) from Zn–Ga alloy at near-room temperature (60 °C). The Zn²⁺-doped γ-Ga₂O₃ NPs were obtained at 60 °C after two steps of ultrasound irradiation (miniaturization and oxidation of Zn–Ga alloy). The specific surface area of Zn²⁺-doped γ-Ga₂O₃ NPs with a zinc content of 4 at.% was 90.4 m²/g. The oxidation behavior of Zn–Ga liquid alloy significantly differed from that of liquid Ga. X-ray photoelectron spectroscopy spectrum and lattice constant of Zn²⁺-doped γ-Ga₂O₃ confirmed Zn²⁺-doping into the γ-Ga₂O₃ crystal structure. By annealing at 900 °C, the obtained Zn²⁺-doped γ-Ga₂O₃ did not transform to Zn²⁺-doped β-Ga₂O₃ but to the mixed phase of β-Ga₂O₃ and ZnGa₂O₄. The results indicate that Zn²⁺ cations, with larger ionic radii than Ga³⁺ cations, are more difficult to be introduced into the β-Ga₂O₃ crystal lattice. Thus, this ultrasound process can potentially synthesize various metal cations-doped γ-Ga₂O₃ NPs without using high temperatures and pressures.