Hydrothermal synthesis of powders in the Ga–Mn–O–H system

Hydrothermal synthesis was used to prepare mixed oxide and oxyhydroxide powders in the Ga–Mn–O–H system. Powders were characterized with X-ray diffraction, thermogravimetric analysis, differential thermal analysis, and scanning electron microscopy with energy dispersive spectroscopy. Samples prepared at pH < 7 contained primarily a diaspore-type phase. Heating of the diapsore-type phase to 900–1000 °C resulted in its conversion to a beta-gallia-type phase for samples prepared with Mn ≤ 0.2 (cation basis) or a spinel-type phase for samples prepared with 0.33 ≤ Mn ≤ 0.56 (cation basis). Unknown phases were produced from samples prepared with Mn = 0.56 (cation basis) at temperatures ranging from 150–180 °C and pH = 9.3–9.6. Heating of the unknowns to 900–1000 °C resulted in their conversion to a spinel-type phase. [Display omitted]