Synthesis and characterization of α-, β-, and γ-Ga2o3 prepared from aqueous solutions by controlled precipitation

alpha, beta and gamma-Ga2O3 have been successfully obtained in an easily scalable synthesis using aqueous solution of gallium nitrate and sodium carbonate as starting materials without any surfactant and additive. alpha and beta-Ga2O3 were obtained by calcination at 350 and 700 degrees C, respectively, of alpha-GaOOH, prepared by controlled precipitation at constant pH 6 and T = 55 degrees C, with 24 h of aging. Aging was necessary to fully convert the initially preciptated gel into a well-crystalline and phase-pure material. gamma-Ga2O3 was obtained after calcination at 500 degrees C of gallia gel, synthesized at constant pH 4 and T = 25 degrees C, without aging. These three polymorphs have a for gallia relatively high surface area: 55 m(2)/g (alpha-Ga2O3), 23 m(2)/g (beta-Ga2O3) and 116 m(2)/g (gamma-Ga2O3). The combination of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), nitrogen physisorption and thermogravimetry (TG) was employed to characterize the samples and their formation. (C) 2012 Elsevier Masson SAS. All rights reserved.