Effects of hot pressing, plasma treatment and electron irradiation on the structure and phase composition of inorganic materials

Methods of infrared spectroscopy, crystal optics, X-ray and chemical analyses have been used to investigate structural-phase transformations in inorganic materials (Si3 N4, Ni O, Fe2 O3) subjected to hot pressing, low-temperature plasma treatment and electron irradiation. A sequential new phase formation has been established in hot pressed silicon nitride (β -Si3 N4) and nickel protoxide (Ni O), depending on the composition of additions (Mg O, CaF2), temperature and environment of the subsequent annealing. The low-temperature plasma treatment causes changes in both the crystal structure and chemical composition of hematite (α - Fe2 O3) and bunsenite (Ni O) with the formation of magnetite (Fe3 O4) and Ni2 O3, respectively. The examination of crystalline β -Si3 N4 samples has revealed the formation of silicon dioxide (Si O2) whereas in amorphous Si3 N4 α -and β -phases were formed. Electron irradiation of the materials was found to cause crystal lattice disordering, redistribution of components and changes in the stoichiometry and phase composition. We have established the new formation of the magnetite (Fe3 O4) and maghemite (high-temperature γ -phase of Fe2 O3) in the irradiated hematite, of nickel oxide Ni2-x O3 and hydroxide films in Ni O, Si2 ON2 oxynitride borders in the crystalline β -Si3 N4, and crystallization α -Si3 N4 and Si2 ON2 in amorphous silicon nitride