Thermal decomposition of gallium nitrate hydrate Ga(NO3)3•xH2O

The thermal decomposition of gallium nitrate hydrate (Ga(NO3)(3)center dot xH(2)O) to gallium oxide has been studied by TG/DTG and DSC measurements performed at different heating rates. It is concluded that 8 water molecules are present in the hydrate compound. The anhydrous gallium nitrate does not form at any temperature as the reaction consists of coupled dehydration/decomposition processes that occur with a mechanism dependent on heating rate. TG measurements performed with isothermal steps (between 31 and 115 degrees C) indicate that Ga(OH)(2)NO3 forms in the first stage of the reaction. Such a compound undergoes further decomposition to Ga(OH)(3) and Ga(NO3)O, compounds that then decompose respectively to Ga(OH)O and finally to Ga2O3 and directly to Ga2O3. Diffuse reflectance Fourier transform IR spectroscopy (DRIFTIR) has been of help in assessing that the reaction consists of parallel dehydration/decomposition processes.