Formation mechanism of rare earth niobates from coprecipitated hydroxides

The charge interaction mechanism of rare earth coprecipitated hydroxides of cerium group and niobium (1:3), based on chemical phase analysis, infrared spectroscopy, thermogravimetry, electron-diffraction and radiography methods is investigated. The nature of X-ray amorphous coprecipitated hydroxides and transformations at heating coprecipitated hydroxides from 20 to 1250 deg are also studied. The coprecipitated hydroxides are shown to be polymer formations of hydroxocomplex type in which rare earth, OH-group and H2O molecule atoms are coordinated to oxygen-niobium frame (rare earth atoms - through oxo- and hydroxobridges). It is established that rare earth niobates are synthesized through an intermediate stage of ortho-niobate formation. Their full transformation into meta-niobates occurs at 1200 deg C and higher