Dielectric properties, structure and morphology during synthesis of β-Ga2O3 by microwave calcination of GaOOH

Abstract The dielectric properties and thermal behaviour of a precursor can provide theoretical support for microwave synthesis related materials and applications. Herein, the properties of both gallium oxide (β-Ga2O3) and gallium oxide hydroxide (α-GaOOH) were studied in detail from 22 °C to 800 °C. The results showed that the dielectric constant (er′) of β-Ga2O3 exhibited an increasing trend with increasing temperature, such a tendency was more obvious after 700 °C, while the dielectric loss (er″) for β-Ga2O3 was continuously reduced to a value of 0.061 (F/m) until 200 °C due to the removal of moisture in the initial stage. Next, er″ for β-Ga2O3 began to increase, reached a maximum value of 0.209 (F/m) at 700 °C, and finally decreased to 0.200 (F/m) at 800 °C. Meanwhile, the calculated loss tangent coefficient of α-GaOOH and β-Ga2O3 indicate that the microwave absorption capabilities of the two substances are approximately equal. Furthermore, the effect of size on dielectric parameters is investigated as the temperature increases. The evolution of morphology and structure was tracked during synthesis of β-Ga2O3 by microwave calcination of α-GaOOH, and results show that the single crystal β-Ga2O3 can be successfully synthesized by microwave calcination to 700 °C for 30 min. This work not only provides some data for the dielectric dispersion behaviour of α-GaOOH and β-Ga2O3, but also proves the feasibility of microwave heating α-GaOOH to prepare β-Ga2O3.