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

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 (beta-Ga2O3) and gallium oxide hydroxide (alpha-GaOOH) were studied in detail from 22 degrees C to 800 degrees C. The results showed that the dielectric constant (epsilon(r)') of beta-Ga2O3 exhibited an increasing trend with increasing temperature, such a tendency was more obvious after 700 degrees C, while the dielectric loss (epsilon(r)') for beta-Ga2O3 was continuously reduced to a value of 0.061 (F/m) until 200 degrees C due to the removal of moisture in the initial stage. Next, epsilon(r)' for beta-Ga2O3 began to increase, reached a maximum value of 0.209 (F/m) at 700 degrees C, and finally decreased to 0.200 (F/m) at 800 degrees C. Meanwhile, the calculated loss tangent coefficient of alpha-GaOOH and beta-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 beta-Ga2O3 by microwave calcination of alpha-GaOOH, and results show that the single crystal beta-Ga2O3 can be successfully synthesized by microwave calcination to 700 degrees C for 30 min. This work not only provides some data for the dielectric dispersion behaviour of alpha-GaOOH and beta-Ga2O3, but also proves the feasibility of microwave heating alpha-GaOOH to prepare beta-Ga2O3.